feat(extension): P2 — WindowGuard Layer 1 (bounce-back)

Replace the WindowGuard stub with the Layer 1 of design §6: any non-
whitelisted window that joins the dashboard workspace is immediately
moved back to the workspace it came from. This single hook catches all
real paths into dashboard -- wmctrl/xdotool moves, super+shift+→
keybind, overview drag-drop, programmatic change_workspace, and initial
window map with _NET_WM_DESKTOP pointing at dashboard.

Implementation:

- Per-window previousWs tracking via WeakMap<Meta.Window, number>,
  updated on each workspace-changed signal whenever the new workspace
  isn't the dashboard. At enable, walk all existing windows and
  pre-populate from their current workspace.
- Bounce target resolution: prefer the recorded workspace; fall back to
  (dashboardIndex - 1), which always exists because WorkspaceWarden
  guarantees dashboard isn't workspace 0.
- Whitelist Set<Meta.Window> with allow()/disallow() so P3's
  ContainerSupervisor can pin the WebKit container without it being
  immediately bounced.
- All signal connections use connectObject/disconnectObject with `this`
  as the tracker, so dispose() unwinds everything in O(1) bookkeeping.
- Override-redirect windows (menus, tooltips) are skipped.

Layers 2 (overview drop refusal), 3 (hide dashboard from switcher
strip), and 4 (Super+Page_Up/Down clamp) are documented in the file
header and deferred to P8/P9 -- they're UX polish that prevents the
*attempt*, while Layer 1 alone meets the P2 acceptance criteria of
"every entry vector bounces".

extension.ts wires WindowGuard up after WorkspaceWarden, in its own
try/catch so a guard init failure leaves the warden disposable.

Build-chain tweak: @girs/gnome-shell augments connectObject onto
GObject.Object via dist/extensions/global.d.ts, but that file isn't
pulled in by `@girs/gnome-shell/ambient`. Adding
`@girs/gnome-shell/extensions/global` to tsconfig "types" loads the
augmentation explicitly.

Verified: `pnpm -r build` and `pnpm -r exec tsc --noEmit` are clean;
extension bundle is 44.8 KB.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

extension/src/extension.ts

@@ -26,10 +26,16 @@ export default class DashwardExtension extends Extension {
       return;
     }
 
-    // P2+ components are still placeholders; left commented until each
-    // phase implements them so we don't pretend to be functional.
-    // this.guard = new WindowGuard();
-    // this.container = new ContainerSupervisor();
+    try {
+      this.guard = new WindowGuard(this.warden);
+    } catch (e) {
+      error(`WindowGuard init failed: ${String(e)}`);
+      // Dashboard workspace exists but is undefended. Continue so disable()
+      // can still tear down the warden cleanly.
+    }
+
+    // P3+ components still placeholders, wired in their own phases.
+    // this.container = new ContainerSupervisor(this.warden, this.guard);
     // this.entry = new EntryUX();
     // this.dbus = new DBusService();
   }