feat(frontend): surfaces live web (workstate live, background, inbox, reconnect) (#13)

Lot F5 du chantier server/client mode : le client web consomme les frames
event.domain (B7) pour animer ses surfaces live.

- webLive.ts : consommation du flux event.domain (workstate, background,
  inbox).
- useLiveReconnect.ts : reconnexion du flux live.
- wsLiveClient.ts / index.ts : câblage du transport live.
- WebWorkspace.tsx : surfaces live branchées.
- Tests : WebWorkspaceLive.test.tsx, wsLiveClientReconnect.test.ts,
  WebApp.test.tsx.

Validé : frontend 753 tests verts, desktop non régressé.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/features/web/WebApp.test.tsx

@@ -102,7 +102,7 @@ describe("WebApp pairing routing", () => {
 
     const snapshot = await screen.findByTestId("web-workstate");
     expect(snapshot.textContent).toContain("Archi");
-    expect(snapshot.textContent).toContain("idle");
+    expect(snapshot.textContent).toContain("Idle");
   });
 
   it("opens a live agent cell for a work-state agent (F4 affordance)", async () => {