fix(chat): retarde le fallback custom→TUI tant que le catalogue agents/profiles est stale (#149)

Cause racine restante après le fix de la course au premier chargement : le
garde-fou de LayoutGrid retombait sur `tui` dès que agents/profiles semblaient
indisponibles, y compris quand le cache était simplement stale (refresh en
cours), écrasant silencieusement la préférence custom. Le fallback n'agit
désormais qu'une fois le catalogue confirmé à jour.

QA verte : LayoutGrid.chat.test.tsx (7 tests), src/features/layout (16
fichiers, 130 tests), cas ciblé "stale catalog refresh".

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

frontend/src/features/layout/LayoutGrid.chat.test.tsx

@@ -254,6 +254,65 @@ describe("LayoutGrid custom agent CLI (#147)", () => {
     expect(window.localStorage.getItem(`idea.agent-cell-mode.p1.${leafId}`)).toBe("custom");
   });
 
+  it("keeps restored custom CLI mode until a stale catalog refresh sees the agent/profile (#149)", async () => {
+    const layout = new MockLayoutGateway();
+    const agent = new MockAgentGateway();
+    const profileGateway = new MockProfileGateway();
+    const terminal = new MockTerminalGateway();
+    const system = new MockSystemGateway();
+    await profileGateway.configureProfiles([structuredProfile]);
+    const created = await agent.createAgent("p1", {
+      name: "Worker",
+      profileId: structuredProfile.id,
+    });
+    const tree = await layout.loadLayout("p1");
+    const leafId = leaves(tree)[0].id;
+    await layout.mutateLayout("p1", {
+      type: "setCellAgent",
+      target: leafId,
+      agent: created.id,
+    });
+    window.localStorage.setItem(`idea.agent-cell-mode.p1.${leafId}`, "custom");
+
+    let staleCatalog = true;
+    const originalListAgents = agent.listAgents.bind(agent);
+    const originalListProfiles = profileGateway.listProfiles.bind(profileGateway);
+    vi.spyOn(agent, "listAgents").mockImplementation(async (projectId) => {
+      if (staleCatalog) return [];
+      return originalListAgents(projectId);
+    });
+    vi.spyOn(profileGateway, "listProfiles").mockImplementation(async () => {
+      if (staleCatalog) return [];
+      return originalListProfiles();
+    });
+
+    renderGrid({
+      layout,
+      agent,
+      profile: profileGateway,
+      terminal,
+      system,
+    } as unknown as Gateways);
+
+    await waitFor(() => expect(screen.getByTestId("layout-leaf")).toBeTruthy());
+    await waitFor(() => expect(agent.listAgents).toHaveBeenCalled());
+    expect(window.localStorage.getItem(`idea.agent-cell-mode.p1.${leafId}`)).toBe("custom");
+    expect(screen.queryByTestId("custom-agent-chat-view")).toBeNull();
+    expect(screen.getByTestId("terminal-view")).toBeTruthy();
+
+    staleCatalog = false;
+    system.emit({
+      type: "agentProfileChanged",
+      agentId: created.id,
+      profileId: structuredProfile.id,
+    });
+
+    await waitFor(() =>
+      expect(screen.getByTestId("custom-agent-chat-view")).toBeTruthy(),
+    );
+    expect(window.localStorage.getItem(`idea.agent-cell-mode.p1.${leafId}`)).toBe("custom");
+  });
+
   it("falls back to native TUI once the catalog confirms the pinned profile is incompatible", async () => {
     const layout = new MockLayoutGateway();
     const agent = new MockAgentGateway();