fix(web): ResourceControls single-scroll, full-height panel, right/down chevrons (#1462) (#1464)

* fix(web): ResourceControls single-scroll + right/down disclosure chevrons (#1462)

Two fixes to the Resources controls panel:

1. Sections scrolled prematurely. `panelMaxHeight` divided the available
   height equally across open sections (`… / n`), so a section with many
   items scrolled while sparse siblings left their equal share unused.
   Replace the per-section ScrollAreas with a single viewport-bounded
   ScrollArea.Autosize around the whole accordion (matching ToolControls /
   PromptControls). Sections size to content; nothing scrolls until the
   open sections' combined height exceeds the cap.

2. Accordion chevrons pointed down/up. Add a `disclosure` Accordion theme
   variant + `.disclosure-chevron[data-rotate]` rule that rotates a
   right-pointing RiArrowRightSLine 90° (not Mantine's default 180°), so
   closed sections point right and open sections point down — matching the
   ResourceLink chevron convention.

Also keep empty (disabled) sections out of the accordion's open set so
they render collapsed with a right chevron instead of an open-but-empty
panel. Verified all states in a real browser via Playwright.

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

* test(web): cover empty-section-collapsed behavior in ResourceControls (#1462)

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

* fix(web): make Resources sidebar fill panel height before scrolling (#1462)

The first pass capped the accordion scroll region at a fixed sub-viewport
height (`100vh - … - 160px`), so the sidebar scrolled before reaching the
height of the detail panel to its right.

Make the sidebar card full-height instead: add a `sidebar` Card variant
(height:100%, flex column, overflow hidden), give it `flex: 1`, and let
ResourceControls' root Stack (`flex: 1; min-height: 0`) and a plain
flex-filling ScrollArea claim the space below the title/search. The card
now matches the detail panel's height exactly and the single inner scroll
region scrolls only once the open sections overflow the full panel.

Adds a ResourcesScreen ManyResources story asserting the sidebar/detail
height match and that overflow scrolls, plus a unit test for the
empty-section-collapsed behavior. Verified heights + scroll in a real
browser via Playwright.

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

* fix(web): pin Resources section headers, scroll each section in place (#1462)

The previous pass scrolled the whole accordion as one block (headers
scrolled away). Restore pinned headers with per-section scrolling, without
the original equal-division premature-scroll bug.

The `disclosure` Accordion now fills its full-height card as a flex column
(`disclosure-sections`): controls are pinned, and each open section's panel
scrolls within its own share of the remaining height. Per-item `flex`
weights (shrink ∝ item count, grow 0) hand space from long sections to
short ones, so nothing scrolls until the combined content overflows the
panel — a long URIs list scrolls in place while Templates stays fully
visible below it. Drops the single outer ScrollArea (and useScrollMemory).

Verified in a real browser: 6 URIs → no scroll, headers pinned, empty
space at the bottom; 40 URIs → URIs panel scrolls in place, Templates
intact, all three headers pinned, sidebar still matches the detail height.

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

* fix(web): Resources sidebar grows with content, capped at screen (#1462)

The `sidebar` Card variant forced `height: 100%`, so the panel was always
full-height with empty space below short content. Switch to
`max-height: 100%` (and drop `flex: 1`) so the card hugs its content and
only caps at the screen height — matching the Tools panel. When content
overflows the cap, the flex accordion still takes over per-section
scrolling with pinned headers.

Verified in a real browser: 6 URIs → card hugs (638px, shorter than the
detail panel); 40 URIs → card caps at the screen (949px == detail),
headers pinned, URIs scrolls in place.

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

* fix(web): preserve empty-section intent + kill accordion collapse jump (#1464 review)

Address review feedback on PR #1464:

- Intent loss (review #1): the accordion's `value` is the filtered
  `visibleOpenSections`, so Mantine's toggle dropped open-but-empty
  sections from the persisted intent. Merge them back in the onChange
  handler so an open empty section stays open and reappears with items.
  Adds a unit test.
- Collapse animation jump (review #3): Mantine's Collapse briefly set the
  panel to its full natural height (fighting the flex layout) on
  open/close, flashing siblings. Set `transitionDuration={0}` so flex
  controls the height; restore a smooth chevron rotation via CSS. Verified
  no jump in a real browser (panel 501→0, no spike). Since closed sections
  now render no content, drop the redundant (and incorrect) "Templates"
  toggle clicks from 4 ResourcesScreen tests (the section is open by
  default) and add a section-toggle test to keep the openSections handler
  covered.
- Nits: scope the stories' chevron query to the accordion root; tighten
  the Collapsed assertion to the identity transform.

Native-vs-styled scrollbar (review #4) split out as #1466.

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

* docs(web): clarify chevron-timing and intent-merge invariants (#1464 review)

Address the two optional doc nits from the re-review:
- Note that the chevron's 200ms restates Mantine's default accordion
  duration (keep in sync if accordion timing is themed).
- Note that the unconditional empty-section merge is safe because
  empty-section controls are disabled, so `next` never contains one.

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

---------

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

clients/web/src/components/groups/ResourceControls/ResourceControls.stories.tsx

@@ -4,9 +4,24 @@ import type {
   ResourceTemplate,
 } from "@modelcontextprotocol/sdk/types.js";
 import type { InspectorResourceSubscription } from "../../../../../../core/mcp/types.js";
-import { fn } from "storybook/test";
+import { expect, fn, within } from "storybook/test";
 import { ResourceControls } from "./ResourceControls";
 
+// rotate(90deg) — Mantine sets `data-rotate` on the chevron slot of an open
+// section; App.css rotates the right-pointing arrow 90° so it points down.
+const ROTATED_DOWN = "matrix(0, 1, -1, 0, 0, 0)";
+// Identity — a closed section's right-pointing chevron at its natural 0°.
+const NOT_ROTATED = "matrix(1, 0, 0, 1, 0, 0)";
+
+function chevronTransforms(canvasElement: HTMLElement): string[] {
+  // Scoped to the accordion root so it still works if a story ever renders more
+  // than one disclosure accordion on the canvas.
+  const root = canvasElement.querySelector(".disclosure-sections");
+  return [
+    ...(root ?? canvasElement).querySelectorAll(".disclosure-chevron"),
+  ].map((c) => getComputedStyle(c).transform);
+}
+
 const meta: Meta<typeof ResourceControls> = {
   title: "Groups/ResourceControls",
   component: ResourceControls,
@@ -65,6 +80,13 @@ export const Default: Story = {
     templates: sampleTemplates,
     subscriptions: sampleSubscriptions,
   },
+  // All three populated sections open by default (compact=false) → every
+  // chevron points down.
+  play: async ({ canvasElement }) => {
+    const transforms = chevronTransforms(canvasElement);
+    expect(transforms).toHaveLength(3);
+    for (const t of transforms) expect(t).toBe(ROTATED_DOWN);
+  },
 };
 
 export const WithSearch: Story = {
@@ -87,3 +109,54 @@ export const Empty: Story = {
     subscriptions: [],
   },
 };
+
+// Sections explicitly collapsed: every chevron points right (no rotation).
+export const Collapsed: Story = {
+  args: {
+    resources: sampleResources,
+    templates: sampleTemplates,
+    subscriptions: sampleSubscriptions,
+    openSections: [],
+  },
+  play: async ({ canvasElement }) => {
+    const transforms = chevronTransforms(canvasElement);
+    expect(transforms).toHaveLength(3);
+    // Identity matrix = the right-pointing arrow's natural 0° (not rotated).
+    for (const t of transforms) expect(t).toBe(NOT_ROTATED);
+  },
+};
+
+// Populated URIs/Templates but no Subscriptions, all "open" in intent. The
+// empty Subscriptions section is kept out of the open set, so its chevron
+// points right while the two populated ones point down.
+export const EmptySectionCollapsed: Story = {
+  args: {
+    resources: sampleResources,
+    templates: sampleTemplates,
+    subscriptions: [],
+    openSections: ["resources", "templates", "subscriptions"],
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    expect(canvas.getByText("Subscriptions (0)")).toBeInTheDocument();
+    const transforms = chevronTransforms(canvasElement);
+    const downCount = transforms.filter((t) => t === ROTATED_DOWN).length;
+    expect(downCount).toBe(2); // URIs + Templates down, Subscriptions right
+  },
+};
+
+// Many URIs with sparse Templates/Subscriptions: under the old equal `/ n`
+// height split, URIs scrolled while the others left their share unused. Now the
+// sections size to content inside one bounded scroll region.
+const manyResources: Resource[] = Array.from({ length: 30 }, (_, i) => ({
+  name: `resource-${String(i + 1).padStart(2, "0")}.md`,
+  uri: `file:///docs/resource-${i + 1}.md`,
+}));
+
+export const ManyResources: Story = {
+  args: {
+    resources: manyResources,
+    templates: sampleTemplates,
+    subscriptions: sampleSubscriptions,
+  },
+};