feat(ui): fenêtres View système séparées — WebviewWindow Tauri + port WindowGateway (#23)

Détache les vues dans de vraies fenêtres système Tauri (multi-écran,
fullscreen). Backend : commandes de gestion de WebviewWindow, capabilities
et composition root. Frontend : nouveau port WindowGateway et son adaptateur
window, entrée panel-only ViewWindow/ViewPanelBody, détachement câblé dans
ProjectsView. QA vert : app-tauri 63, frontend typecheck + vitest 546/546.

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

frontend/src/adapters/window.test.ts

@@ -0,0 +1,71 @@
+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 { TauriWindowGateway } from "./window";
+
+describe("TauriWindowGateway (#23)", () => {
+  beforeEach(() => {
+    invoke.mockReset().mockResolvedValue({});
+    listen.mockReset();
+  });
+
+  it("open/close relay camelCase payloads to the backend commands", async () => {
+    const gw = new TauriWindowGateway();
+    await gw.openViewWindow("tickets", "proj-1");
+    expect(invoke).toHaveBeenCalledWith("open_view_window", {
+      panel: "tickets",
+      projectId: "proj-1",
+    });
+    await gw.closeViewWindow("git", "proj-2");
+    expect(invoke).toHaveBeenCalledWith("close_view_window", {
+      panel: "git",
+      projectId: "proj-2",
+    });
+  });
+
+  it("onViewWindowClosed listens on the lifecycle channel and forwards only closes", async () => {
+    // Capture the raw Tauri listener so we can drive lifecycle events at will.
+    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 TauriWindowGateway();
+    const handler = vi.fn();
+    const off = await gw.onViewWindowClosed(handler);
+
+    expect(listen).toHaveBeenCalledWith(
+      "view-window://lifecycle",
+      expect.any(Function),
+    );
+
+    // opened / focused are dropped…
+    raw?.({
+      payload: { kind: "opened", panel: "git", projectId: "p", label: "view-git-p" },
+    });
+    raw?.({
+      payload: { kind: "focused", panel: "git", projectId: "p", label: "view-git-p" },
+    });
+    expect(handler).not.toHaveBeenCalled();
+
+    // …only closed reaches the port handler, narrowed to { panel, projectId }.
+    raw?.({
+      payload: { kind: "closed", panel: "git", projectId: "p", label: "view-git-p" },
+    });
+    expect(handler).toHaveBeenCalledTimes(1);
+    expect(handler).toHaveBeenCalledWith({ panel: "git", projectId: "p" });
+
+    off();
+    expect(unlisten).toHaveBeenCalled();
+  });
+});