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/app/ViewWindow.test.tsx

@@ -0,0 +1,62 @@
+/**
+ * #23 — the panel-only entry. `parseViewWindowParams` validates the
+ * `?panel=&project=` query, and `ViewWindow` resolves the project through the
+ * gateway then renders only the requested view (here: the tickets view).
+ */
+import { describe, it, expect } from "vitest";
+import { render, screen, waitFor } from "@testing-library/react";
+
+import { DIProvider } from "@/app/di";
+import {
+  MockAgentGateway,
+  MockProjectGateway,
+  MockSystemGateway,
+  MockTicketGateway,
+} from "@/adapters/mock";
+import type { Gateways } from "@/ports";
+import { ViewWindow, parseViewWindowParams } from "./ViewWindow";
+
+describe("parseViewWindowParams (#23)", () => {
+  it("parses a valid panel + project", () => {
+    expect(parseViewWindowParams("?panel=tickets&project=p-1")).toEqual({
+      panel: "tickets",
+      projectId: "p-1",
+    });
+  });
+
+  it("rejects a missing project, missing panel, or the non-detachable projects panel", () => {
+    expect(parseViewWindowParams("?panel=tickets")).toBeNull();
+    expect(parseViewWindowParams("?project=p-1")).toBeNull();
+    expect(parseViewWindowParams("?panel=projects&project=p-1")).toBeNull();
+    expect(parseViewWindowParams("?panel=bogus&project=p-1")).toBeNull();
+    expect(parseViewWindowParams("")).toBeNull();
+  });
+});
+
+describe("ViewWindow (#23)", () => {
+  it("resolves the project and renders only the requested view", async () => {
+    const system = new MockSystemGateway();
+    const project = new MockProjectGateway();
+    const created = await project.createProject("alpha", "/p/a");
+    const gateways = {
+      system,
+      project,
+      agent: new MockAgentGateway(),
+      ticket: new MockTicketGateway(system),
+    } as unknown as Gateways;
+
+    render(
+      <DIProvider gateways={gateways}>
+        <ViewWindow panel="tickets" projectId={created.id} />
+      </DIProvider>,
+    );
+
+    // The window chrome shows the panel title and the resolved project name.
+    expect(screen.getByRole("heading", { name: "Tickets" })).toBeTruthy();
+    await waitFor(() => expect(screen.getByText("· alpha")).toBeTruthy());
+    // The tickets view itself mounted (its search box is present).
+    await waitFor(() =>
+      expect(screen.getByLabelText("search tickets")).toBeTruthy(),
+    );
+  });
+});