feat(agent): UI hot-swap de profil (A2) — commande Tauri + sélecteur + dialog

- Tauri : commande change_agent_profile + ChangeAgentProfileRequestDto/Dto
  (camelCase, relaunchedSession omis si None), câblage state.rs par composition.
- Front : gateway changeAgentProfile (adapters Tauri+mock), sélecteur de profil
  par agent, dialog de confirmation FR (« Changer le moteur abandonne l'historique
  de conversation… »), refresh sur event agentProfileChanged.

Tests : app-tauri dto 5/5 ; vitest 314/314 (mapping, payload, dialog gating,
libellé FR, refresh). 0 régression.

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

frontend/src/features/agents/agents.test.tsx

@@ -390,6 +390,125 @@ describe("MockAgentGateway (unit)", () => {
   });
 });
 
+// ---------------------------------------------------------------------------
+// A2 — profile hot-swap selector + confirmation dialog
+// ---------------------------------------------------------------------------
+
+/** Seeds two profiles so an agent's engine can be swapped to a different one. */
+async function seededProfiles(): Promise<MockProfileGateway> {
+  const profile = new MockProfileGateway();
+  await profile.configureProfiles([
+    {
+      id: "prof-1",
+      name: "Claude Code",
+      command: "claude",
+      args: [],
+      contextInjection: { strategy: "conventionFile", target: "CLAUDE.md" },
+      detect: null,
+      cwdTemplate: "{projectRoot}",
+    },
+    {
+      id: "prof-2",
+      name: "Codex CLI",
+      command: "codex",
+      args: [],
+      contextInjection: { strategy: "conventionFile", target: "AGENTS.md" },
+      detect: null,
+      cwdTemplate: "{projectRoot}",
+    },
+  ]);
+  return profile;
+}
+
+describe("AgentsPanel profile hot-swap (A2)", () => {
+  it("changing the profile select does NOT call changeAgentProfile immediately — it opens a confirmation dialog", async () => {
+    const agent = new MockAgentGateway();
+    await agent.createAgent(PROJECT_ID, { name: "Swap", profileId: "prof-1" });
+    const swapSpy = vi.spyOn(agent, "changeAgentProfile");
+
+    renderPanel(agent, await seededProfiles());
+    await waitForIdle();
+    await screen.findByText("Swap");
+
+    const select = screen.getByLabelText("profile for Swap") as HTMLSelectElement;
+    fireEvent.change(select, { target: { value: "prof-2" } });
+
+    // No gateway call yet — only the dialog appears.
+    expect(swapSpy).not.toHaveBeenCalled();
+    expect(screen.getByRole("dialog")).toBeTruthy();
+  });
+
+  it("Cancel closes the dialog without calling changeAgentProfile", async () => {
+    const agent = new MockAgentGateway();
+    await agent.createAgent(PROJECT_ID, { name: "Swap", profileId: "prof-1" });
+    const swapSpy = vi.spyOn(agent, "changeAgentProfile");
+
+    renderPanel(agent, await seededProfiles());
+    await waitForIdle();
+    await screen.findByText("Swap");
+
+    fireEvent.change(screen.getByLabelText("profile for Swap"), {
+      target: { value: "prof-2" },
+    });
+    fireEvent.click(
+      screen.getByRole("button", { name: "cancel profile change" }),
+    );
+
+    await waitFor(() => expect(screen.queryByRole("dialog")).toBeNull());
+    expect(swapSpy).not.toHaveBeenCalled();
+  });
+
+  it("Continue confirms and calls changeAgentProfile with the chosen profile", async () => {
+    const agent = new MockAgentGateway();
+    const created = await agent.createAgent(PROJECT_ID, {
+      name: "Swap",
+      profileId: "prof-1",
+    });
+    const swapSpy = vi.spyOn(agent, "changeAgentProfile");
+
+    renderPanel(agent, await seededProfiles());
+    await waitForIdle();
+    await screen.findByText("Swap");
+
+    fireEvent.change(screen.getByLabelText("profile for Swap"), {
+      target: { value: "prof-2" },
+    });
+    fireEvent.click(
+      screen.getByRole("button", { name: "confirm profile change" }),
+    );
+
+    await waitFor(() => {
+      expect(swapSpy).toHaveBeenCalled();
+      expect(swapSpy.mock.calls[0][0]).toBe(PROJECT_ID);
+      expect(swapSpy.mock.calls[0][1]).toBe(created.id);
+      expect(swapSpy.mock.calls[0][2]).toBe("prof-2");
+    });
+    // Dialog closes after confirmation.
+    await waitFor(() => expect(screen.queryByRole("dialog")).toBeNull());
+  });
+
+  it("the confirmation dialog message is in FRENCH and conveys the spec §15.1 wording", async () => {
+    const agent = new MockAgentGateway();
+    await agent.createAgent(PROJECT_ID, { name: "Swap", profileId: "prof-1" });
+
+    renderPanel(agent, await seededProfiles());
+    await waitForIdle();
+    await screen.findByText("Swap");
+
+    fireEvent.change(screen.getByLabelText("profile for Swap"), {
+      target: { value: "prof-2" },
+    });
+
+    const dialog = screen.getByRole("dialog");
+    const text = dialog.textContent ?? "";
+    // Spec §15.1: « Changer le moteur abandonne l'historique de conversation
+    // (le contexte et la mémoire sont conservés). Continuer ? » — must be FRENCH.
+    expect(text).toMatch(/abandonne l'historique de conversation/i);
+    expect(text).toMatch(/contexte et la mémoire sont conservés/i);
+    expect(text).toMatch(/Continuer\s*\?/);
+  });
+});
+
 describe("AgentsPanel live refresh on domain events", () => {
   it("refreshes the list when an `agentLaunched` event fires (out-of-band creation)", async () => {
     const agent = new MockAgentGateway();
@@ -423,6 +542,38 @@ describe("AgentsPanel live refresh on domain events", () => {
     expect(await screen.findByText("Orchestrated")).toBeTruthy();
   });
 
+  it("refreshes the list when an `agentProfileChanged` event fires (A2 hot-swap)", async () => {
+    const agent = new MockAgentGateway();
+    const profile = new MockProfileGateway();
+    const system = new MockSystemGateway();
+    const template = new MockTemplateGateway(agent);
+    const gateways = { agent, profile, system, template } as unknown as Gateways;
+
+    const created = await agent.createAgent(PROJECT_ID, {
+      name: "Swapper",
+      profileId: "p1",
+    });
+
+    render(
+      <DIProvider gateways={gateways}>
+        <AgentsPanel projectId={PROJECT_ID} projectRoot="/home/me/proj" />
+      </DIProvider>,
+    );
+    await waitFor(() => expect(screen.getByText("Swapper")).toBeTruthy());
+
+    // Mutate the profile out of band, then emit the event the backend relays.
+    await agent.changeAgentProfile(PROJECT_ID, created.id, "p2", 24, 80);
+    const refreshSpy = vi.spyOn(agent, "listAgents");
+    system.emit({
+      type: "agentProfileChanged",
+      agentId: created.id,
+      profileId: "p2",
+    });
+
+    // The hook re-fetches the list on the event.
+    await waitFor(() => expect(refreshSpy).toHaveBeenCalled());
+  });
+
   it("does not crash when the system gateway is absent", async () => {
     // The existing renderPanel helper injects no `system` gateway; the
     // subscription effect must no-op rather than throw.