fix(web): enable websocket proxying in vite dev server

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

web/vite.config.ts

@@ -18,7 +18,9 @@ export default defineConfig({
   },
   server: {
     proxy: {
-      "/api": { target: backendTarget, changeOrigin: true },
+      // ws:true is required for the terminal WebSocket to be proxied to the
+      // Go backend in dev. http-only proxies strip the Upgrade header.
+      "/api": { target: backendTarget, changeOrigin: true, ws: true },
       "/healthz": { target: backendTarget, changeOrigin: true },
     },
   },