feat(servers): export server list as mcp.json download (#1346) (#1351)

* feat(servers): export server list as mcp.json download (#1346)

Adds an Export button to the Servers screen, next to "Add Servers".
Clicking it downloads the current server list as a canonical mcp.json
file (2-space indent, same shape serializeStore writes), so the user
can hand it off, sync it to another machine, or symlink into Claude
Desktop / Cursor / Cline.

Wiring:
- ServerListControls: new Export Button (variant=default), disabled
  when serverCount === 0 (nothing to download).
- ServerListScreen / InspectorView: thread `onExport` / `onServerExport`
  through.
- App.tsx: onServerExport runs serverEntriesToMcpConfig on the in-memory
  servers list, JSON.stringify with 2-space indent, and triggers a Blob
  download via a temporary anchor (appended to body for Firefox
  compatibility, then removed; object URL revoked).

Tests:
- ServerListControls unit tests cover button-count (toggle hidden vs
  shown, Export always present), disabled-on-empty, click fires onExport.
- ServerListControls.stories grows play functions for both stories —
  WithServers asserts Export is enabled + click fires the spy in real
  Chromium, WithoutServers asserts Export is disabled.
- Existing screen + view tests / stories updated for the new prop.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(servers): address PR #1351 review (extract helpers + exception safety + guard)

Substantive items from the review:

1. Serialization format parity (review #1): added
   `serializeMcpConfig(entries)` to core/mcp/serverList.ts — a
   browser-safe helper that runs `serverEntriesToMcpConfig` then
   stringifies with 2-space indent. Single source of truth for export
   formatting; can't drift from serializeStore's on-disk shape.

2. Exception safety on the anchor cleanup (review #2) + a direct test
   for the App.tsx download wiring (review #6): extracted
   `downloadJsonFile(filename, json)` to clients/web/src/lib/
   downloadFile.ts. removeChild + revokeObjectURL run in a `finally`
   so a thrown click() doesn't leak the DOM node or the object URL.
   Unit-tested under happy-dom with URL.createObjectURL mocked
   (happy-dom doesn't ship it).

3. Empty-list guard (review #5): App.tsx onServerExport bails when
   `servers.length === 0`. The button's disabled prop already prevents
   the UI path, but the handler is now locally correct against any
   future programmatic caller (storybook, keyboard shortcut, etc.).

Acknowledged but not changed:
- Tooltip on the disabled Export button (review #3) — Mantine's
  disabled-button + Tooltip wart wants a span wrapper + custom events
  config. Optional per the reviewer; deferred.
- Repeated exports → `mcp (1).json` browser suffix (review #4) — a
  deliberate trade-off since `mcp.json` is the conventional name a user
  would expect to symlink into Claude Desktop / Cursor / etc.

Tests: 1647 unit (+6) + 410 integration + 306 storybook = 2363 green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -1,5 +1,5 @@
 import type { Meta, StoryObj } from "@storybook/react-vite";
-import { fn } from "storybook/test";
+import { expect, fn, userEvent, within } from "storybook/test";
 import { ServerListControls } from "./ServerListControls";
 
 const meta: Meta<typeof ServerListControls> = {
@@ -18,6 +18,17 @@ export const WithServers: Story = {
     onAddManually: fn(),
     onImportConfig: fn(),
     onImportServerJson: fn(),
+    onExport: fn(),
+  },
+  play: async ({ canvasElement, args }) => {
+    // Real-Chromium regression guard: Export is enabled when servers exist,
+    // and clicking it fires onExport. Unit tests cover the same path under
+    // happy-dom; this catches anything browser-specific in the wiring.
+    const body = within(canvasElement.ownerDocument.body);
+    const exportBtn = await body.findByRole("button", { name: /Export/ });
+    await expect(exportBtn).not.toBeDisabled();
+    await userEvent.click(exportBtn);
+    await expect(args.onExport).toHaveBeenCalledTimes(1);
   },
 };
 
@@ -29,5 +40,11 @@ export const WithoutServers: Story = {
     onAddManually: fn(),
     onImportConfig: fn(),
     onImportServerJson: fn(),
+    onExport: fn(),
+  },
+  play: async ({ canvasElement }) => {
+    const body = within(canvasElement.ownerDocument.body);
+    const exportBtn = await body.findByRole("button", { name: /Export/ });
+    await expect(exportBtn).toBeDisabled();
   },
 };

clients/web/src/components/groups/ServerListControls/ServerListControls.test.tsx

@@ -10,19 +10,23 @@ const baseProps = {
   onAddManually: vi.fn(),
   onImportConfig: vi.fn(),
   onImportServerJson: vi.fn(),
+  onExport: vi.fn(),
 };
 
 describe("ServerListControls", () => {
-  it("hides the list toggle when there are no servers", () => {
+  it("hides the list toggle when there are no servers (Export + Add Servers remain)", () => {
     renderWithMantine(<ServerListControls {...baseProps} />);
     const buttons = screen.getAllByRole("button");
-    expect(buttons).toHaveLength(1);
-    expect(buttons[0]).toHaveAccessibleName(/Add Servers/);
+    expect(buttons).toHaveLength(2);
+    expect(screen.getByRole("button", { name: /Export/ })).toBeInTheDocument();
+    expect(
+      screen.getByRole("button", { name: /Add Servers/ }),
+    ).toBeInTheDocument();
   });
 
-  it("shows the list toggle when servers exist", () => {
+  it("shows the list toggle alongside Export + Add Servers when servers exist", () => {
     renderWithMantine(<ServerListControls {...baseProps} serverCount={2} />);
-    expect(screen.getAllByRole("button")).toHaveLength(2);
+    expect(screen.getAllByRole("button")).toHaveLength(3);
   });
 
   it("calls onToggleList when the list toggle is clicked", async () => {
@@ -39,4 +43,24 @@ describe("ServerListControls", () => {
     await user.click(buttons[0]);
     expect(onToggleList).toHaveBeenCalledTimes(1);
   });
+
+  it("disables Export when the list is empty (nothing to download)", () => {
+    renderWithMantine(<ServerListControls {...baseProps} />);
+    expect(screen.getByRole("button", { name: /Export/ })).toBeDisabled();
+  });
+
+  it("enables Export when at least one server exists", () => {
+    renderWithMantine(<ServerListControls {...baseProps} serverCount={1} />);
+    expect(screen.getByRole("button", { name: /Export/ })).not.toBeDisabled();
+  });
+
+  it("calls onExport when Export is clicked (with at least one server)", async () => {
+    const user = userEvent.setup();
+    const onExport = vi.fn();
+    renderWithMantine(
+      <ServerListControls {...baseProps} serverCount={1} onExport={onExport} />,
+    );
+    await user.click(screen.getByRole("button", { name: /Export/ }));
+    expect(onExport).toHaveBeenCalledTimes(1);
+  });
 });

clients/web/src/components/groups/ServerListControls/ServerListControls.tsx

@@ -1,4 +1,4 @@
-import { Group } from "@mantine/core";
+import { Button, Group } from "@mantine/core";
 import { ListToggle } from "../../elements/ListToggle/ListToggle";
 import {
   ServerAddMenu,
@@ -9,6 +9,8 @@ export interface ServerListControlsProps extends AddServerMenuProps {
   compact: boolean;
   serverCount: number;
   onToggleList: () => void;
+  /** Download the current server list as a canonical `mcp.json` file. */
+  onExport: () => void;
 }
 
 export function ServerListControls({
@@ -18,12 +20,16 @@ export function ServerListControls({
   onAddManually,
   onImportConfig,
   onImportServerJson,
+  onExport,
 }: ServerListControlsProps) {
   return (
     <Group justify="flex-end">
       {serverCount > 0 && (
         <ListToggle compact={compact} onToggle={onToggleList} />
       )}
+      <Button variant="default" onClick={onExport} disabled={serverCount === 0}>
+        Export
+      </Button>
       <ServerAddMenu
         onAddManually={onAddManually}
         onImportConfig={onImportConfig}