[claude] Add service worker for true offline capability (#212) (#215)

Co-authored-by: Claude (Opus 4.6) <claude@hermes.local>
Co-committed-by: Claude (Opus 4.6) <claude@hermes.local>

index.html

@@ -48,6 +48,11 @@
 
   <div id="sovereignty-msg">⚡ SOVEREIGNTY ⚡</div>
 
+  <script>
+    if ('serviceWorker' in navigator) {
+      navigator.serviceWorker.register('/sw.js').catch(() => {});
+    }
+  </script>
   <script type="module" src="app.js"></script>
 <div id="loading" style="position: fixed; top: 0; left: 0; right: 0; height: 4px; background: #222; z-index: 1000;">
   <div id="loading-bar" style="height: 100%; background: var(--color-accent); width: 0;"></div>

sw.js

@@ -0,0 +1,96 @@
+// The Nexus — Service Worker
+// Cache-first for assets, network-first for API calls
+
+const CACHE_NAME = 'nexus-v1';
+const ASSET_CACHE = 'nexus-assets-v1';
+
+const CORE_ASSETS = [
+  '/',
+  '/index.html',
+  '/app.js',
+  '/style.css',
+  '/manifest.json',
+  '/ws-client.js',
+  'https://unpkg.com/three@0.183.0/build/three.module.js',
+  'https://unpkg.com/three@0.183.0/examples/jsm/controls/OrbitControls.js',
+  'https://unpkg.com/three@0.183.0/examples/jsm/postprocessing/EffectComposer.js',
+  'https://unpkg.com/three@0.183.0/examples/jsm/postprocessing/RenderPass.js',
+  'https://unpkg.com/three@0.183.0/examples/jsm/postprocessing/UnrealBloomPass.js',
+  'https://unpkg.com/three@0.183.0/examples/jsm/postprocessing/ShaderPass.js',
+  'https://unpkg.com/three@0.183.0/examples/jsm/shaders/CopyShader.js',
+  'https://unpkg.com/three@0.183.0/examples/jsm/shaders/LuminosityHighPassShader.js',
+];
+
+// Install: precache core assets
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(ASSET_CACHE).then((cache) => cache.addAll(CORE_ASSETS))
+      .then(() => self.skipWaiting())
+  );
+});
+
+// Activate: clean up old caches
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(
+        keys
+          .filter((key) => key !== CACHE_NAME && key !== ASSET_CACHE)
+          .map((key) => caches.delete(key))
+      )
+    ).then(() => self.clients.claim())
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  const { request } = event;
+  const url = new URL(request.url);
+
+  // Network-first for API calls (Gitea / WebSocket upgrades / portals.json live data)
+  if (
+    url.pathname.startsWith('/api/') ||
+    url.hostname.includes('143.198.27.163') ||
+    request.headers.get('Upgrade') === 'websocket'
+  ) {
+    event.respondWith(networkFirst(request));
+    return;
+  }
+
+  // Cache-first for everything else (local assets + CDN)
+  event.respondWith(cacheFirst(request));
+});
+
+async function cacheFirst(request) {
+  const cached = await caches.match(request);
+  if (cached) return cached;
+
+  try {
+    const response = await fetch(request);
+    if (response.ok) {
+      const cache = await caches.open(ASSET_CACHE);
+      cache.put(request, response.clone());
+    }
+    return response;
+  } catch {
+    // Offline and not cached — return a minimal fallback for navigation
+    if (request.mode === 'navigate') {
+      const fallback = await caches.match('/index.html');
+      if (fallback) return fallback;
+    }
+    return new Response('Offline', { status: 503, statusText: 'Service Unavailable' });
+  }
+}
+
+async function networkFirst(request) {
+  try {
+    const response = await fetch(request);
+    if (response.ok) {
+      const cache = await caches.open(CACHE_NAME);
+      cache.put(request, response.clone());
+    }
+    return response;
+  } catch {
+    const cached = await caches.match(request);
+    return cached || new Response('Offline', { status: 503, statusText: 'Service Unavailable' });
+  }
+}