feat(frontend): host les fenêtres plugin et l'API publique windows.open

Ajoute la vue window host qui charge le layout plugin dans une fenêtre OS
détachée, expose react/react-dom/jsx-runtime hébergés sous
frontend/public/plugin-host pour que le runtime SDK y résolve React, et
câble services.windows.open() côté runtime plugin (loader/services/registry).

npm test -- --run src/adapters/window.test.ts src/app/ViewWindow.test.tsx
  src/plugins/runtime/loader.test.ts src/plugins/runtime/services.test.ts : 39/39
npm run typecheck : OK
npm run build : OK

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

frontend/src/adapters/window.ts

@@ -15,6 +15,8 @@ import { listen } from "@tauri-apps/api/event";
 
 import type { Unsubscribe } from "@/domain";
 import type {
+  PluginLayoutWindowOpenInput,
+  PluginLayoutWindowOpenResult,
   ViewWindowClosed,
   ViewWindowSnapshot,
   WindowGateway,
@@ -41,6 +43,14 @@ export class TauriWindowGateway implements WindowGateway {
     await invoke("open_view_window", { panel });
   }
 
+  async openPluginLayoutWindow(
+    input: PluginLayoutWindowOpenInput,
+  ): Promise<PluginLayoutWindowOpenResult> {
+    return invoke<PluginLayoutWindowOpenResult>("open_plugin_layout_window", {
+      input,
+    });
+  }
+
   async closeViewWindow(panel: string): Promise<void> {
     await invoke("close_view_window", { panel });
   }