fix(windows): fenêtres de panneau détachées suivent le projet en focus côté UI (#47)

Partie frontend. Ajoute un adaptateur focusedProject et un port dédié : la
ViewWindow détachée n'est plus liée à un project_id figé, elle s'abonne à
l'event focused-project émis par la fenêtre principale et affiche le panneau
du projet courant. ProjectsView propage le focus ; le détachement crée une
fenêtre panel-only. Couvert par les tests window/ViewWindow/focusedProject/
ProjectsView.focus.

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

frontend/src/adapters/focusedProject.test.ts

@@ -0,0 +1,76 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+const invoke = vi.fn();
+const listen = vi.fn();
+vi.mock("@tauri-apps/api/core", () => ({
+  invoke: (...args: unknown[]) => invoke(...args),
+}));
+vi.mock("@tauri-apps/api/event", () => ({
+  listen: (...args: unknown[]) => listen(...args),
+}));
+
+import { TauriFocusedProjectGateway } from "./focusedProject";
+
+describe("TauriFocusedProjectGateway (#47)", () => {
+  beforeEach(() => {
+    invoke.mockReset().mockResolvedValue(null);
+    listen.mockReset();
+  });
+
+  it("set/get relay to the backend focused-project commands", async () => {
+    const gw = new TauriFocusedProjectGateway();
+
+    await gw.setFocusedProject({ id: "p1", name: "alpha", root: "/p/a" });
+    expect(invoke).toHaveBeenCalledWith("set_focused_project", {
+      project: { id: "p1", name: "alpha", root: "/p/a" },
+    });
+
+    await gw.setFocusedProject(null);
+    expect(invoke).toHaveBeenCalledWith("set_focused_project", {
+      project: null,
+    });
+
+    invoke.mockResolvedValueOnce({ id: "p2", name: "beta", root: "/p/b" });
+    await expect(gw.getFocusedProject()).resolves.toEqual({
+      id: "p2",
+      name: "beta",
+      root: "/p/b",
+    });
+    expect(invoke).toHaveBeenCalledWith("get_focused_project");
+
+    // A `null`/undefined focus normalises to `null`.
+    invoke.mockResolvedValueOnce(null);
+    await expect(gw.getFocusedProject()).resolves.toBeNull();
+  });
+
+  it("onFocusedProjectChanged listens on the channel and forwards the project (or null)", async () => {
+    let raw: ((e: { payload: unknown }) => void) | undefined;
+    const unlisten = vi.fn();
+    listen.mockImplementation((_name: string, cb: typeof raw) => {
+      raw = cb;
+      return Promise.resolve(unlisten);
+    });
+
+    const gw = new TauriFocusedProjectGateway();
+    const handler = vi.fn();
+    const off = await gw.onFocusedProjectChanged(handler);
+
+    expect(listen).toHaveBeenCalledWith(
+      "focused-project://changed",
+      expect.any(Function),
+    );
+
+    raw?.({ payload: { project: { id: "p1", name: "alpha", root: "/p/a" } } });
+    expect(handler).toHaveBeenLastCalledWith({
+      id: "p1",
+      name: "alpha",
+      root: "/p/a",
+    });
+
+    raw?.({ payload: { project: null } });
+    expect(handler).toHaveBeenLastCalledWith(null);
+
+    off();
+    expect(unlisten).toHaveBeenCalled();
+  });
+});