feat: Electron desktop app — hardening, IPC bridge, and dev launch fixes

- Dev/prod URL auto-detection (Vite 5173 in dev, server 3000 in prod)
- Typed IPC bridge via preload (notifications, badge, window controls, updates, deep links)
- Native OS notifications via NotificationController with window focus suppression
- Auto-update via electron-updater with UpdateToast UI
- Deep linking (backspace:// protocol) for macOS and Windows/Linux
- Window state persistence (position, size, maximize across restarts)
- Tray icon with graceful fallback when icon asset missing
- Suppress PWA service worker polling/reloads inside Electron
- Platform detection layer (isElectron, getElectronAPI)
- Root workspace scripts (dev:desktop, build:desktop)
- Document BACKSPACE_URL and BACKSPACE_UPDATE_URL env vars

packages/web/src/platform/deepLink.ts

@@ -0,0 +1,49 @@
+import { useEffect } from 'react';
+import { useNavigate } from 'react-router-dom';
+import { isElectron } from './platform';
+
+/**
+ * Listens for deep link events from the Electron main process and navigates accordingly.
+ *
+ * Supported routes:
+ *   backspace://join/{code}            → /join/{code}
+ *   backspace://join/{code}@{host}     → /join/{code}@{host}
+ *   backspace://channel/{spaceId}/{channelId} → /channels/{spaceId}/{channelId}
+ */
+export function useDeepLinkHandler(): void {
+  const navigate = useNavigate();
+
+  useEffect(() => {
+    if (!isElectron()) return;
+
+    const api = window.backspace!;
+    api.onDeepLink((url: string) => {
+      let parsed: URL;
+      try {
+        parsed = new URL(url);
+      } catch {
+        console.warn('[DeepLink] Invalid URL:', url);
+        return;
+      }
+
+      if (parsed.protocol !== 'backspace:') return;
+
+      // URL host + pathname gives us the route
+      // backspace://join/code  → host="join", pathname="/code"
+      // backspace://channel/spaceId/channelId → host="channel", pathname="/spaceId/channelId"
+      const host = parsed.hostname;
+      const pathParts = parsed.pathname.split('/').filter(Boolean);
+
+      if (host === 'join' && pathParts.length >= 1) {
+        const code = pathParts[0]!;
+        navigate(`/join/${code}`);
+      } else if (host === 'channel' && pathParts.length >= 2) {
+        const spaceId = pathParts[0]!;
+        const channelId = pathParts[1]!;
+        navigate(`/channels/${spaceId}/${channelId}`);
+      } else {
+        console.warn('[DeepLink] Unknown route:', url);
+      }
+    });
+  }, [navigate]);
+}

packages/web/src/platform/electron.d.ts

@@ -0,0 +1,32 @@
+/** Type augmentation for the Electron IPC bridge exposed by preload.ts */
+
+interface BackspaceElectronAPI {
+  // Platform info
+  platform: NodeJS.Platform;
+
+  // Window controls
+  minimize: () => void;
+  maximize: () => void;
+  close: () => void;
+
+  // Notifications & badge
+  showNotification: (title: string, body: string) => void;
+  setBadgeCount: (count: number) => void;
+
+  // Auto-update (Task 2.1)
+  onUpdateAvailable: (callback: (info: { version: string }) => void) => void;
+  onUpdateDownloaded: (callback: (info: { version: string }) => void) => void;
+  onUpdateError: (callback: (error: string) => void) => void;
+  installUpdate: () => void;
+  checkForUpdates: () => void;
+
+  // Window focus (Task 2.2)
+  onWindowFocusChange: (callback: (focused: boolean) => void) => void;
+
+  // Deep linking (Task 2.3)
+  onDeepLink: (callback: (url: string) => void) => void;
+}
+
+interface Window {
+  backspace?: BackspaceElectronAPI;
+}

packages/web/src/platform/notifications.ts

@@ -0,0 +1,21 @@
+import { isElectron } from './platform';
+
+export function sendNotification(title: string, body: string): void {
+  if (isElectron()) {
+    window.backspace!.showNotification(title, body);
+  } else if ('Notification' in window && Notification.permission === 'granted') {
+    new Notification(title, { body, icon: '/icons/icon-192.png' });
+  }
+}
+
+export function requestNotificationPermission(): Promise<boolean> {
+  if (isElectron()) return Promise.resolve(true);
+  if (!('Notification' in window)) return Promise.resolve(false);
+  return Notification.requestPermission().then((p) => p === 'granted');
+}
+
+export function updateBadgeCount(count: number): void {
+  if (isElectron()) {
+    window.backspace!.setBadgeCount(count);
+  }
+}

packages/web/src/platform/platform.ts

@@ -0,0 +1,7 @@
+export function isElectron(): boolean {
+  return typeof window !== 'undefined' && typeof window.backspace !== 'undefined';
+}
+
+export function getElectronAPI(): BackspaceElectronAPI | null {
+  return window.backspace ?? null;
+}