add audio scribe sample (#1475)

* add audio scribe sample

* Fix wrong parameter name

* Cleanup and more robust audio scribe

* better manifest descriptions

* demo chat app clean up

functional-samples/ai.gemini-on-device-audio-scribe/sidepanel.js

@@ -0,0 +1,78 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/* global LanguageModel */
+
+chrome.runtime.onMessage.addListener(async ({ data }) => {
+  let content;
+  try {
+    if (data.type != 'audio-scribe' || !data || !isValidUrl(data.objectUrl)) {
+      return;
+    }
+    // Check if it's an audio file
+    const audio = await fetch(data.objectUrl);
+    content = await audio.blob();
+    if (!content.type || !content.type.startsWidth('audio/')) {
+      return;
+    }
+  } catch (e) {
+    console.log(e);
+  }
+
+  // Setup message UI
+  const messages = document.getElementById('messages');
+  const li = document.createElement('li');
+  li.append('...');
+  messages.append(li);
+
+  try {
+    // Transcribe audio
+    const availability = await LanguageModel.availability();
+    if (availability !== 'available') {
+      console.error('Model is', availability);
+      throw new Error('Model is not available');
+    }
+    const session = await LanguageModel.create({
+      expectedInputs: [{ type: 'audio' }]
+    });
+    const stream = session.promptStreaming([
+      { type: 'audio', content },
+      'transcribe this audio'
+    ]);
+
+    // Render streamed response
+    let first = true;
+    for await (const chunk of stream) {
+      if (first) {
+        li.textContent = '';
+        first = false;
+      }
+      li.append(chunk);
+    }
+  } catch (error) {
+    console.log(error);
+    li.textContent = error.message;
+  }
+});
+
+function isValidUrl(string) {
+  let url;
+
+  try {
+    url = new URL(string);
+    return true;
+  } catch (_) {
+    return false;
+  }
+}