Add Ghostty terminal, session recovery, voice asset caching, and gitignore large assets

Integrates ghostty-web and node-pty packages, adds tmux session recovery on startup,
refactors WebSocket transport to noServer mode, caches Sherpa voice model assets via
service worker. Large assets (sherpa, ghostty-vt.wasm, fonts) are now gitignored as
they are copied from the webterm project.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/transport/websocket-transport.ts

@@ -22,11 +22,10 @@ export class WebSocketTransport extends EventEmitter {
   // connection is never terminated before it has a chance to respond.
   private alive = new WeakMap<WebSocket, boolean>();
 
-  /** Create WebSocketServer on /ws path with JWT verification and ping/pong keepalive. */
-  setup(server: HttpServer | HttpsServer): void {
+  /** Create WebSocketServer in noServer mode. Call handleUpgrade() from your server upgrade handler. */
+  setup(_server: HttpServer | HttpsServer): void {
     this.wss = new WebSocketServer({
-      server,
-      path: '/ws',
+      noServer: true,
       verifyClient: ({ req }, cb) => {
         const url = new URL(req.url!, `http://${req.headers.host}`);
         const token = url.searchParams.get('token');
@@ -73,6 +72,13 @@ export class WebSocketTransport extends EventEmitter {
     this.pingInterval.unref();
   }
 
+  /** Route an HTTP upgrade request into this WSS (called from server's upgrade handler). */
+  handleUpgrade(req: import('http').IncomingMessage, socket: import('stream').Duplex, head: Buffer): void {
+    this.wss!.handleUpgrade(req, socket, head, (ws) => {
+      this.wss!.emit('connection', ws, req);
+    });
+  }
+
   /** Shut down the WebSocket server and stop keepalive. */
   destroy(): void {
     if (this.pingInterval) {