feat(web): pin Logging/History/Network as a resizable column (#1616)

Add the ability to "pin" the Logging, History, and Network screens into a
second column on the right of the InspectorView, so a primary screen and a
monitor screen are visible at once (e.g. watch Logs while calling a Tool).

- A "pin as column" button on the Logs/History/Network panel toolbars opens
  the column (shown only when wide + connected).
- The column hosts a MonitoringControls tab row (available monitor tabs +
  close) over the selected embedded screen. Pinning removes the monitor group
  from the header tab bar; closing (x) returns it.
- The divider between the primary area and the column is draggable (pointer +
  keyboard); width is clamped and persisted.
- The split collapses to one column below ~1040px (the ServerListScreen
  single-card breakpoint) and while disconnected, without discarding the pin
  preference — it reopens when wide + connected again.

State (pinned/tab/width) is view-local and persisted via the existing
useLocalStorage pattern, so no new props thread through App and ViewHeader is
unchanged (it just receives a filtered tab list). Screens/panels gain an
`embedded` mode (fills the parent height, drops the 340px filter sidebar) via a
shared EmbeddableScrollArea element.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/web/src/components/elements/EmbeddableScrollArea/EmbeddableScrollArea.stories.tsx

@@ -0,0 +1,43 @@
+import { createRef } from "react";
+import { Stack, Text } from "@mantine/core";
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { expect, within } from "storybook/test";
+import { EmbeddableScrollArea } from "./EmbeddableScrollArea";
+
+const meta: Meta<typeof EmbeddableScrollArea> = {
+  title: "Elements/EmbeddableScrollArea",
+  component: EmbeddableScrollArea,
+};
+
+export default meta;
+type Story = StoryObj<typeof EmbeddableScrollArea>;
+
+const rows = Array.from({ length: 40 }, (_, i) => (
+  <Text key={i}>Row {i + 1}</Text>
+));
+
+export const FullSize: Story = {
+  render: () => (
+    <EmbeddableScrollArea embedded={false} viewportRef={createRef()}>
+      <Stack gap="xs">{rows}</Stack>
+    </EmbeddableScrollArea>
+  ),
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    expect(canvas.getByText("Row 1")).toBeInTheDocument();
+  },
+};
+
+export const Embedded: Story = {
+  render: () => (
+    <Stack h={240} gap={0}>
+      <EmbeddableScrollArea embedded viewportRef={createRef()}>
+        <Stack gap="xs">{rows}</Stack>
+      </EmbeddableScrollArea>
+    </Stack>
+  ),
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    expect(canvas.getByText("Row 1")).toBeInTheDocument();
+  },
+};

clients/web/src/components/elements/EmbeddableScrollArea/EmbeddableScrollArea.test.tsx

@@ -0,0 +1,34 @@
+import { createRef } from "react";
+import { describe, it, expect } from "vitest";
+import { renderWithMantine, screen } from "../../../test/renderWithMantine";
+import { EmbeddableScrollArea } from "./EmbeddableScrollArea";
+
+describe("EmbeddableScrollArea", () => {
+  it("renders its children full-size", () => {
+    renderWithMantine(
+      <EmbeddableScrollArea embedded={false} viewportRef={createRef()}>
+        <div>full-size content</div>
+      </EmbeddableScrollArea>,
+    );
+    expect(screen.getByText("full-size content")).toBeInTheDocument();
+  });
+
+  it("renders its children when embedded", () => {
+    renderWithMantine(
+      <EmbeddableScrollArea embedded={true} viewportRef={createRef()}>
+        <div>embedded content</div>
+      </EmbeddableScrollArea>,
+    );
+    expect(screen.getByText("embedded content")).toBeInTheDocument();
+  });
+
+  it("attaches the viewport ref to the scroll viewport", () => {
+    const ref = createRef<HTMLDivElement>();
+    renderWithMantine(
+      <EmbeddableScrollArea embedded={false} viewportRef={ref}>
+        <div>content</div>
+      </EmbeddableScrollArea>,
+    );
+    expect(ref.current).toBeInstanceOf(HTMLElement);
+  });
+});

clients/web/src/components/elements/EmbeddableScrollArea/EmbeddableScrollArea.tsx

@@ -0,0 +1,56 @@
+import type { ReactNode, Ref } from "react";
+import { ScrollArea, Stack } from "@mantine/core";
+
+// Full-size, the monitor stream panels bound their scroll to the viewport
+// minus the header and the panel's own chrome.
+const FULLSIZE_MAH =
+  "calc(100vh - var(--app-shell-header-height, 0px) - 150px)";
+
+export interface EmbeddableScrollAreaProps {
+  /**
+   * True when rendered inside the pinned monitoring column (#1616): the scroll
+   * region fills its flex parent instead of using the viewport calc. A
+   * `flex:1 / mih:0` wrapper caps the inner `ScrollArea` at the space remaining
+   * below the column's controls (via `mah:100%`), so no viewport math is needed
+   * and the final rows never clip.
+   */
+  embedded: boolean;
+  viewportRef: Ref<HTMLDivElement>;
+  children: ReactNode;
+}
+
+/**
+ * The scroll region shared by the Logs / History / Network stream panels, which
+ * render both full-size (their own tab) and embedded (the monitoring column).
+ * Centralizes the one layout difference between those two hosts.
+ */
+export function EmbeddableScrollArea({
+  embedded,
+  viewportRef,
+  children,
+}: EmbeddableScrollAreaProps) {
+  if (embedded) {
+    return (
+      <Stack flex={1} mih={0} gap={0}>
+        <ScrollArea.Autosize
+          viewportRef={viewportRef}
+          mah="100%"
+          type="scroll"
+          offsetScrollbars
+        >
+          {children}
+        </ScrollArea.Autosize>
+      </Stack>
+    );
+  }
+  return (
+    <ScrollArea.Autosize
+      viewportRef={viewportRef}
+      mah={FULLSIZE_MAH}
+      type="scroll"
+      offsetScrollbars
+    >
+      {children}
+    </ScrollArea.Autosize>
+  );
+}

clients/web/src/components/elements/PinColumnButton/PinColumnButton.stories.tsx

@@ -0,0 +1,21 @@
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { expect, fn, within } from "storybook/test";
+import { PinColumnButton } from "./PinColumnButton";
+
+const meta: Meta<typeof PinColumnButton> = {
+  title: "Elements/PinColumnButton",
+  component: PinColumnButton,
+  args: { onPin: fn() },
+};
+
+export default meta;
+type Story = StoryObj<typeof PinColumnButton>;
+
+export const Default: Story = {
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    expect(
+      canvas.getByRole("button", { name: "Pin as column" }),
+    ).toBeInTheDocument();
+  },
+};

clients/web/src/components/elements/PinColumnButton/PinColumnButton.test.tsx

@@ -0,0 +1,21 @@
+import { describe, it, expect, vi } from "vitest";
+import userEvent from "@testing-library/user-event";
+import { renderWithMantine, screen } from "../../../test/renderWithMantine";
+import { PinColumnButton } from "./PinColumnButton";
+
+describe("PinColumnButton", () => {
+  it("renders a labelled pin-as-column button", () => {
+    renderWithMantine(<PinColumnButton onPin={vi.fn()} />);
+    expect(
+      screen.getByRole("button", { name: "Pin as column" }),
+    ).toBeInTheDocument();
+  });
+
+  it("invokes onPin when clicked", async () => {
+    const user = userEvent.setup();
+    const onPin = vi.fn();
+    renderWithMantine(<PinColumnButton onPin={onPin} />);
+    await user.click(screen.getByRole("button", { name: "Pin as column" }));
+    expect(onPin).toHaveBeenCalledTimes(1);
+  });
+});

clients/web/src/components/elements/PinColumnButton/PinColumnButton.tsx

@@ -0,0 +1,26 @@
+import { ActionIcon } from "@mantine/core";
+import { TbLayoutSidebarRightExpand } from "react-icons/tb";
+
+export interface PinColumnButtonProps {
+  /** Pin this screen into the monitoring column to the right. */
+  onPin: () => void;
+}
+
+/**
+ * Toolbar icon that pins the owning monitor screen (Logs / History / Network)
+ * into the resizable column on the right of the InspectorView (#1616). Distinct
+ * from `PinToggle` (which pins individual history entries) — this one opens a
+ * side column, so it uses a right-sidebar glyph and an "as column" label.
+ */
+export function PinColumnButton({ onPin }: PinColumnButtonProps) {
+  return (
+    <ActionIcon
+      variant="default"
+      size="lg"
+      aria-label="Pin as column"
+      onClick={onPin}
+    >
+      <TbLayoutSidebarRightExpand size={18} />
+    </ActionIcon>
+  );
+}

clients/web/src/components/elements/ResizeHandle/ResizeHandle.stories.tsx

@@ -0,0 +1,51 @@
+import { useState } from "react";
+import { Box, Group, Text } from "@mantine/core";
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { expect, within } from "storybook/test";
+import { ResizeHandle } from "./ResizeHandle";
+
+const meta: Meta<typeof ResizeHandle> = {
+  title: "Elements/ResizeHandle",
+  component: ResizeHandle,
+};
+
+export default meta;
+type Story = StoryObj<typeof ResizeHandle>;
+
+// A minimal split so the handle has a panel to resize in the docs view. The
+// panel sits to the right; dragging the handle left widens it.
+function ResizeDemo() {
+  const [width, setWidth] = useState(320);
+  const [dragWidth, setDragWidth] = useState<number | null>(null);
+  return (
+    <Group h={200} gap={0} wrap="nowrap">
+      <Box flex={1} bg="var(--inspector-surface-subtle)" p="md">
+        <Text>Primary</Text>
+      </Box>
+      <ResizeHandle
+        value={dragWidth ?? width}
+        min={200}
+        max={520}
+        onChange={setDragWidth}
+        onCommit={(next) => {
+          setWidth(next);
+          setDragWidth(null);
+        }}
+        aria-label="Resize demo panel"
+      />
+      <Box w={dragWidth ?? width} p="md" bg="var(--inspector-surface-card)">
+        <Text>Column ({dragWidth ?? width}px)</Text>
+      </Box>
+    </Group>
+  );
+}
+
+export const Default: Story = {
+  render: () => <ResizeDemo />,
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    expect(
+      canvas.getByRole("separator", { name: "Resize demo panel" }),
+    ).toBeInTheDocument();
+  },
+};

clients/web/src/components/elements/ResizeHandle/ResizeHandle.test.tsx

@@ -0,0 +1,144 @@
+import { describe, it, expect, vi, afterEach } from "vitest";
+import {
+  renderWithMantine,
+  screen,
+  fireEvent,
+} from "../../../test/renderWithMantine";
+import { ResizeHandle } from "./ResizeHandle";
+
+// The panel sits to the RIGHT of the handle, so moving the pointer LEFT
+// (decreasing clientX) widens it: next = startWidth + (startX - clientX).
+function setup(overrides: Partial<Parameters<typeof ResizeHandle>[0]> = {}) {
+  const onChange = vi.fn();
+  const onCommit = vi.fn();
+  renderWithMantine(
+    <ResizeHandle
+      value={400}
+      min={320}
+      max={720}
+      onChange={onChange}
+      onCommit={onCommit}
+      {...overrides}
+    />,
+  );
+  return { handle: screen.getByRole("separator"), onChange, onCommit };
+}
+
+describe("ResizeHandle", () => {
+  afterEach(() => {
+    document.body.classList.remove("resizing-col");
+  });
+
+  it("exposes the separator role with live aria values", () => {
+    const { handle } = setup();
+    expect(handle).toHaveAttribute("aria-orientation", "vertical");
+    expect(handle).toHaveAttribute("aria-valuenow", "400");
+    expect(handle).toHaveAttribute("aria-valuemin", "320");
+    expect(handle).toHaveAttribute("aria-valuemax", "720");
+    expect(handle).toHaveAccessibleName("Resize panel");
+  });
+
+  it("accepts a custom aria-label", () => {
+    setup({ "aria-label": "Resize monitoring column" });
+    expect(
+      screen.getByRole("separator", { name: "Resize monitoring column" }),
+    ).toBeInTheDocument();
+  });
+
+  it("reports the widened value while dragging left and commits on release", () => {
+    const { handle, onChange, onCommit } = setup();
+    fireEvent.pointerDown(handle, { clientX: 500, pointerId: 1 });
+    fireEvent.pointerMove(handle, { clientX: 460, pointerId: 1 });
+    // startWidth 400 + (500 - 460) = 440
+    expect(onChange).toHaveBeenLastCalledWith(440);
+    expect(onCommit).not.toHaveBeenCalled();
+    fireEvent.pointerUp(handle, { clientX: 460, pointerId: 1 });
+    expect(onCommit).toHaveBeenCalledWith(440);
+  });
+
+  it("clamps to max when dragged past the upper bound", () => {
+    const { handle, onChange } = setup();
+    fireEvent.pointerDown(handle, { clientX: 500, pointerId: 1 });
+    fireEvent.pointerMove(handle, { clientX: 0, pointerId: 1 });
+    expect(onChange).toHaveBeenLastCalledWith(720);
+  });
+
+  it("clamps to min when dragged past the lower bound", () => {
+    const { handle, onChange } = setup();
+    fireEvent.pointerDown(handle, { clientX: 500, pointerId: 1 });
+    fireEvent.pointerMove(handle, { clientX: 900, pointerId: 1 });
+    expect(onChange).toHaveBeenLastCalledWith(320);
+  });
+
+  it("toggles the drag body class across the gesture", () => {
+    const { handle } = setup();
+    fireEvent.pointerDown(handle, { clientX: 500, pointerId: 1 });
+    expect(document.body.classList.contains("resizing-col")).toBe(true);
+    fireEvent.pointerUp(handle, { clientX: 500, pointerId: 1 });
+    expect(document.body.classList.contains("resizing-col")).toBe(false);
+  });
+
+  it("ends the drag on pointer cancel", () => {
+    const { handle, onCommit } = setup();
+    fireEvent.pointerDown(handle, { clientX: 500, pointerId: 1 });
+    fireEvent.pointerCancel(handle, { clientX: 480, pointerId: 1 });
+    expect(onCommit).toHaveBeenCalledWith(420);
+    expect(document.body.classList.contains("resizing-col")).toBe(false);
+  });
+
+  it("ignores pointer moves when no drag is active", () => {
+    const { handle, onChange, onCommit } = setup();
+    fireEvent.pointerMove(handle, { clientX: 460, pointerId: 1 });
+    fireEvent.pointerUp(handle, { clientX: 460, pointerId: 1 });
+    expect(onChange).not.toHaveBeenCalled();
+    expect(onCommit).not.toHaveBeenCalled();
+  });
+
+  it("uses pointer capture when the platform supports it", () => {
+    const setCapture = vi.fn();
+    const releaseCapture = vi.fn();
+    const proto = HTMLElement.prototype as unknown as {
+      setPointerCapture?: (id: number) => void;
+      releasePointerCapture?: (id: number) => void;
+    };
+    proto.setPointerCapture = setCapture;
+    proto.releasePointerCapture = releaseCapture;
+    try {
+      const { handle } = setup();
+      fireEvent.pointerDown(handle, { clientX: 500, pointerId: 7 });
+      fireEvent.pointerUp(handle, { clientX: 500, pointerId: 7 });
+      expect(setCapture).toHaveBeenCalledWith(7);
+      expect(releaseCapture).toHaveBeenCalledWith(7);
+    } finally {
+      delete proto.setPointerCapture;
+      delete proto.releasePointerCapture;
+    }
+  });
+
+  it("widens by one step on ArrowLeft and commits", () => {
+    const { handle, onChange, onCommit } = setup({ step: 20 });
+    fireEvent.keyDown(handle, { key: "ArrowLeft" });
+    expect(onChange).toHaveBeenCalledWith(420);
+    expect(onCommit).toHaveBeenCalledWith(420);
+  });
+
+  it("narrows by one step on ArrowRight", () => {
+    const { handle, onChange } = setup();
+    fireEvent.keyDown(handle, { key: "ArrowRight" });
+    // default step 16: 400 - 16 = 384
+    expect(onChange).toHaveBeenCalledWith(384);
+  });
+
+  it("clamps keyboard steps to the bounds", () => {
+    const { handle, onChange } = setup({ value: 712 });
+    fireEvent.keyDown(handle, { key: "ArrowLeft" });
+    expect(onChange).toHaveBeenCalledWith(720);
+  });
+
+  it("ignores non-arrow keys", () => {
+    const { handle, onChange, onCommit } = setup();
+    fireEvent.keyDown(handle, { key: "Enter" });
+    expect(onChange).not.toHaveBeenCalled();
+    expect(onCommit).not.toHaveBeenCalled();
+  });
+});

clients/web/src/components/elements/ResizeHandle/ResizeHandle.tsx

@@ -0,0 +1,107 @@
+import { useRef, type KeyboardEvent, type PointerEvent } from "react";
+import { Box } from "@mantine/core";
+
+export interface ResizeHandleProps {
+  /** Current width (px) of the panel this handle resizes. */
+  value: number;
+  /** Lower / upper clamp bounds (px). */
+  min: number;
+  max: number;
+  /** Keyboard arrow step in px (default 16). */
+  step?: number;
+  /**
+   * Fired continuously while dragging and on each keyboard step, with the
+   * clamped next width. The parent renders from this for live feedback.
+   */
+  onChange: (next: number) => void;
+  /**
+   * Fired once when the gesture ends (pointer up / key up) with the final
+   * clamped width, so the parent can persist it in a single write.
+   */
+  onCommit: (next: number) => void;
+  "aria-label"?: string;
+}
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.min(max, Math.max(min, value));
+}
+
+/**
+ * A thin draggable vertical divider that resizes a panel sitting to its RIGHT
+ * (so dragging left widens the panel). Pointer-capture keeps the gesture alive
+ * even when the pointer crosses an iframe (the Apps screen renders one), which
+ * would otherwise swallow the move stream and make the drag stick. Exposes the
+ * ARIA `separator` role with live value so it's operable by keyboard too.
+ */
+export function ResizeHandle({
+  value,
+  min,
+  max,
+  step = 16,
+  onChange,
+  onCommit,
+  "aria-label": ariaLabel = "Resize panel",
+}: ResizeHandleProps) {
+  // Gesture origin, captured on pointer down. `null` while idle.
+  const drag = useRef<{ startX: number; startWidth: number } | null>(null);
+
+  function handlePointerDown(e: PointerEvent<HTMLDivElement>) {
+    drag.current = { startX: e.clientX, startWidth: value };
+    // Optional chaining: happy-dom (unit tests) doesn't implement pointer
+    // capture, and it's a progressive enhancement, not required for correctness.
+    e.currentTarget.setPointerCapture?.(e.pointerId);
+    document.body.classList.add("resizing-col");
+  }
+
+  function handlePointerMove(e: PointerEvent<HTMLDivElement>) {
+    if (!drag.current) return;
+    const next = clamp(
+      drag.current.startWidth + (drag.current.startX - e.clientX),
+      min,
+      max,
+    );
+    onChange(next);
+  }
+
+  function endDrag(e: PointerEvent<HTMLDivElement>) {
+    if (!drag.current) return;
+    const next = clamp(
+      drag.current.startWidth + (drag.current.startX - e.clientX),
+      min,
+      max,
+    );
+    drag.current = null;
+    e.currentTarget.releasePointerCapture?.(e.pointerId);
+    document.body.classList.remove("resizing-col");
+    onCommit(next);
+  }
+
+  function handleKeyDown(e: KeyboardEvent<HTMLDivElement>) {
+    // Left widens (panel is on the right), Right narrows — mirrors the drag.
+    const delta =
+      e.key === "ArrowLeft" ? step : e.key === "ArrowRight" ? -step : 0;
+    if (delta === 0) return;
+    e.preventDefault();
+    const next = clamp(value + delta, min, max);
+    onChange(next);
+    onCommit(next);
+  }
+
+  return (
+    <Box
+      role="separator"
+      aria-orientation="vertical"
+      aria-valuenow={value}
+      aria-valuemin={min}
+      aria-valuemax={max}
+      aria-label={ariaLabel}
+      tabIndex={0}
+      className="resize-handle"
+      onPointerDown={handlePointerDown}
+      onPointerMove={handlePointerMove}
+      onPointerUp={endDrag}
+      onPointerCancel={endDrag}
+      onKeyDown={handleKeyDown}
+    />
+  );
+}