Add WebGPU probe timeout for static demo

app.js

@@ -114,6 +114,7 @@ const MIN_VAD_SILENCE_MS = 200;
 const MAX_VAD_SILENCE_MS = 800;
 const DEFAULT_LOOPBACK_SPEED = 1.10;
 const MIC_START_TIMEOUT_MS = 15000;
+const WEBGPU_ADAPTER_TIMEOUT_MS = 5000;
 const DEFAULT_TTS_CHUNKING = Object.freeze({
   firstSentenceMinChars: 5,
   sentenceMinChars: 8,
@@ -587,7 +588,11 @@ async function supportsWebGPU() {
     return false;
   }
   try {
-    const adapter = await navigator.gpu.requestAdapter();
+    const adapter = await withTimeout(
+      navigator.gpu.requestAdapter(),
+      WEBGPU_ADAPTER_TIMEOUT_MS,
+      "WebGPU adapter probe",
+    );
     state.webgpuAvailable = Boolean(adapter);
     state.webgpuAdapterInfo = await readGpuAdapterInfo(adapter);
     state.webgpuAdapterFeatures = adapter?.features ? [...adapter.features].sort() : [];
@@ -850,6 +855,18 @@ async function getUserMediaWithTimeout(constraints, timeoutMs = MIC_START_TIMEOU
   return stream;
 }
 
+function withTimeout(promise, timeoutMs, label) {
+  let timeoutId = 0;
+  return Promise.race([
+    promise.finally(() => window.clearTimeout(timeoutId)),
+    new Promise((_, reject) => {
+      timeoutId = window.setTimeout(() => {
+        reject(new Error(`${label} timed out after ${(timeoutMs / 1000).toFixed(0)} seconds.`));
+      }, timeoutMs);
+    }),
+  ]);
+}
+
 function stopMic() {
   if (!state.micActive) return;
   state.micActive = false;