feat: add service worker for PWA support (offline caching, installability)

- Add sw.js with stale-while-revalidate caching for static assets
- Network-first for HTML navigation, skip API/WS requests
- Register service worker in main.tsx on page load
- Enhanced manifest.json with orientation, categories, and all icon sizes
- App is now installable as a standalone PWA on mobile and desktop

public/manifest.json

@@ -1,12 +1,24 @@
 {
   "name": "PinchChat",
   "short_name": "PinchChat",
-  "description": "A sleek, dark-themed webchat UI for OpenClaw",
+  "description": "A sleek, dark-themed webchat UI for OpenClaw — monitor sessions, stream responses, and inspect tool calls in real-time.",
   "start_url": "/",
   "display": "standalone",
   "background_color": "#1e1e24",
   "theme_color": "#1e1e24",
+  "orientation": "any",
+  "categories": ["developer", "productivity", "utilities"],
   "icons": [
+    {
+      "src": "/favicon-16.png",
+      "sizes": "16x16",
+      "type": "image/png"
+    },
+    {
+      "src": "/favicon-32.png",
+      "sizes": "32x32",
+      "type": "image/png"
+    },
     {
       "src": "/logo-192.png",
       "sizes": "192x192",

public/sw.js

@@ -0,0 +1,62 @@
+// PinchChat Service Worker — cache static assets for offline/instant load
+const CACHE_NAME = 'pinchchat-v1';
+
+// Cache static assets on install
+self.addEventListener('install', (event) => {
+  self.skipWaiting();
+});
+
+// Clean old caches on activate
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(keys.filter((k) => k !== CACHE_NAME).map((k) => caches.delete(k)))
+    )
+  );
+  self.clients.claim();
+});
+
+// Stale-while-revalidate for static assets, network-first for API/WS
+self.addEventListener('fetch', (event) => {
+  const url = new URL(event.request.url);
+
+  // Skip non-GET, WebSocket upgrades, and chrome-extension requests
+  if (event.request.method !== 'GET') return;
+  if (url.protocol === 'chrome-extension:') return;
+
+  // Don't cache API calls or WebSocket-related requests
+  if (url.pathname.startsWith('/api') || url.pathname.startsWith('/ws')) return;
+
+  // For navigation requests (HTML), always go network-first to get latest SPA shell
+  if (event.request.mode === 'navigate') {
+    event.respondWith(
+      fetch(event.request)
+        .then((response) => {
+          const clone = response.clone();
+          caches.open(CACHE_NAME).then((cache) => cache.put(event.request, clone));
+          return response;
+        })
+        .catch(() => caches.match(event.request))
+    );
+    return;
+  }
+
+  // Static assets (JS, CSS, images, fonts): stale-while-revalidate
+  if (
+    url.pathname.match(/\.(js|css|png|jpg|jpeg|gif|webp|svg|woff2?|ttf|ico|json)$/) ||
+    url.pathname.startsWith('/assets/')
+  ) {
+    event.respondWith(
+      caches.open(CACHE_NAME).then((cache) =>
+        cache.match(event.request).then((cached) => {
+          const fetchPromise = fetch(event.request).then((response) => {
+            if (response.ok) cache.put(event.request, response.clone());
+            return response;
+          });
+          return cached || fetchPromise;
+        })
+      )
+    );
+    return;
+  }
+});