feat(web): reorderable ServerCards — drag-and-drop + keyboard (#1369) (#1447)

* feat(web): reorderable ServerCards — drag-and-drop + keyboard (#1369)

Let users control the order of servers on the Servers screen instead of
hand-editing mcp.json. Each ServerCard gets a grip handle (in the header,
left of the name) that drives an @dnd-kit sortable; pointer and keyboard
sensors both work, with live-region announcements for screen readers.

- Backend: PUT /api/servers/order rewrites mcp.json in the supplied order
  inside the write lock, reusing the atomic-write + watcher-notify path.
  Registered before /:id so "order" isn't captured as a server id. Rejects
  with 409 when the id set no longer matches disk and 400 on duplicate /
  malformed bodies, so a reorder racing an external edit can't drop or
  duplicate an entry.
- Hook: useServers.reorderServers(orderedIds) — optimistic local reorder,
  PUT, refresh-to-disk-truth on failure.
- UI: SortableServerCard wrapper owns the dnd-kit concerns; ServerListScreen
  wraps the grid in DndContext + SortableContext (rect strategy) with
  pointer + keyboard sensors and announcements. Reorder math and a11y copy
  extracted to reorderIds.ts / serverReorder.ts for direct unit testing.
  Renders plain cards (no grip) when no onReorder is wired.
- Wired onServerReorder through InspectorView -> App.tsx.

Tests: pure-helper units, hook (persist / optimistic / 409 revert), 9
backend integration tests (incl. id-set-mismatch rejection and the
route-registration guard), ServerCard/ServerListScreen units, and a
real-browser Storybook keyboard-reorder play (the dnd-kit keyboard sensor
needs layout rects that happy-dom doesn't provide).

Adds @dnd-kit/core, @dnd-kit/sortable, @dnd-kit/utilities.

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

* fix(web): notify on reorder failure; skip reorder glue when not reorderable

Address PR #1447 review:
- App.tsx: catch reorderServers rejection (409 from a racing external edit,
  or a network error) and show a red toast, matching the error-handling
  pattern used by every other mutation — previously the rejection was
  discarded with `void` and the drag silently bounced back.
- ServerListScreen: only build handleDragEnd / announcements when
  `reorderable`, so the four-closure announcements object isn't allocated
  every render when no onReorder is wired.

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/views/InspectorView/InspectorView.stories.tsx

@@ -356,6 +356,7 @@ const meta: Meta<typeof InspectorView> = {
     onServerEdit: fn(),
     onServerClone: fn(),
     onServerRemove: fn(),
+    onServerReorder: fn(),
     serverSupportsTaskToolCalls: false,
     onToolsUiChange: fn(),
     onCallTool: fn(),

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

@@ -88,6 +88,7 @@ function makeProps(
     onServerEdit: vi.fn(),
     onServerClone: vi.fn(),
     onServerRemove: vi.fn(),
+    onServerReorder: vi.fn(),
     serverSupportsTaskToolCalls: false,
     onToolsUiChange: vi.fn(),
     onCallTool: vi.fn(),

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

@@ -268,6 +268,8 @@ export interface InspectorViewProps {
   onServerEdit: (id: string) => void;
   onServerClone: (id: string) => void;
   onServerRemove: (id: string) => void;
+  /** Persist a new server ordering (drag-and-drop / keyboard reorder). */
+  onServerReorder: (orderedIds: string[]) => void;
 
   // Per-primitive actions (route to `inspectorClient` methods / hook refresh).
   // Each `on{Screen}UiChange` persists that screen's lifted UI state (#1417).
@@ -380,6 +382,7 @@ export function InspectorView({
   onServerEdit,
   onServerClone,
   onServerRemove,
+  onServerReorder,
   serverSupportsTaskToolCalls,
   onToolsUiChange,
   onCallTool,
@@ -549,6 +552,7 @@ export function InspectorView({
               onEdit={onServerEdit}
               onClone={onServerClone}
               onRemove={onServerRemove}
+              onReorder={onServerReorder}
               compact={serversCompact}
               onToggleCompact={() => setServersCompact((c) => !c)}
             />