fix(settings): complete a close left unanswered by settings teardown

Leaving settings and closing the window in the same instant could race:
the renderer's close-request listener was gone while its fire-and-forget
disarm was still in flight, so a close intercepted in that window was
silently swallowed. The guard is mount-long in the renderer, so a
disarm can only mean settings is gone and its form already settled —
the main process now completes the pending intercepted intent (close or
quit) when a disarm finds one unanswered.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/electron-backend/src/app/services/window-close-guard.service.spec.ts

@@ -258,6 +258,38 @@ describe('WindowCloseGuard', () => {
         expect(win.fireClose()).toBe(false);
     });
 
+    it('completes a close left unanswered when the renderer disarms', () => {
+        // Teardown race: close intercepted, then the settings page is torn
+        // down and disarms before answering — the close must not be
+        // swallowed.
+        const { guard, win } = createArmedGuard();
+
+        win.fireClose();
+        guard.setGuardActive(false);
+
+        expect(win.close).toHaveBeenCalledTimes(1);
+    });
+
+    it('resumes an unanswered quit when the renderer disarms', () => {
+        const { app, guard, win } = createArmedGuard();
+
+        app.fireBeforeQuit();
+        win.fireClose();
+        guard.setGuardActive(false);
+
+        expect(app.quit).toHaveBeenCalledTimes(1);
+        expect(win.close).not.toHaveBeenCalled();
+    });
+
+    it('closes nothing on a plain disarm without a pending intent', () => {
+        const { app, guard, win } = createArmedGuard();
+
+        guard.setGuardActive(false);
+
+        expect(win.close).not.toHaveBeenCalled();
+        expect(app.quit).not.toHaveBeenCalled();
+    });
+
     it('drops an unanswered quit intent when the renderer navigates away', () => {
         const { app, guard, win } = createArmedGuard();
 

apps/electron-backend/src/app/services/window-close-guard.service.ts

@@ -101,6 +101,17 @@ export class WindowCloseGuard {
 
     setGuardActive(active: boolean): void {
         this.guardActive = active;
+
+        // A disarm with an unanswered intercepted close is the teardown
+        // race: the renderer left settings between the interception and
+        // this disarm reaching us, so nobody remains to confirm and the
+        // user's close would be silently swallowed. The guard is mount-long
+        // in the renderer, so a disarm only ever means "settings is gone" —
+        // its form was already settled by the router guard, nothing is left
+        // to protect, and the intercepted intent can complete.
+        if (!active && this.pendingIntent !== null) {
+            this.confirmClose();
+        }
     }
 
     /**