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/views/InspectorView/InspectorView.stories.tsx

@@ -294,6 +294,7 @@ const meta: Meta<typeof InspectorView> = {
     onServerAdd: fn(),
     onServerImportConfig: fn(),
     onServerImportJson: fn(),
+    onServerExport: fn(),
     onServerInfo: fn(),
     onServerSettings: fn(),
     onServerEdit: fn(),

clients/web/src/components/views/InspectorView/InspectorView.test.tsx

@@ -58,6 +58,7 @@ function makeProps(
     onServerAdd: vi.fn(),
     onServerImportConfig: vi.fn(),
     onServerImportJson: vi.fn(),
+    onServerExport: vi.fn(),
     onServerInfo: vi.fn(),
     onServerSettings: vi.fn(),
     onServerEdit: vi.fn(),

clients/web/src/components/views/InspectorView/InspectorView.tsx

@@ -154,6 +154,8 @@ export interface InspectorViewProps {
   onServerAdd: () => void;
   onServerImportConfig: () => void;
   onServerImportJson: () => void;
+  /** Download the current server list as a canonical `mcp.json` file. */
+  onServerExport: () => void;
   onServerInfo: (id: string) => void;
   onServerSettings: (id: string) => void;
   onServerEdit: (id: string) => void;
@@ -233,6 +235,7 @@ export function InspectorView({
   onServerAdd,
   onServerImportConfig,
   onServerImportJson,
+  onServerExport,
   onServerInfo,
   onServerSettings,
   onServerEdit,
@@ -356,6 +359,7 @@ export function InspectorView({
               onAddManually={onServerAdd}
               onImportConfig={onServerImportConfig}
               onImportServerJson={onServerImportJson}
+              onExport={onServerExport}
               onToggleConnection={onToggleConnection}
               onServerInfo={onServerInfo}
               onSettings={onServerSettings}