feat: Research: NotebookLM — create audio overview of SOUL.md as podcast (#293)

Refs #293
Agent: groq

app.js

@@ -2732,6 +2732,10 @@ document.getElementById('podcast-toggle').addEventListener('click', () => {
         utterance.lang = 'en-US';
         utterance.rate = 0.9;
         utterance.pitch = 0.9;
+        utterance.onend = () => {
+          document.getElementById('podcast-toggle').disabled = false;
+        };
+        document.getElementById('podcast-toggle').disabled = true;
         speechSynthesis.speak(utterance);
       })
       .catch(err => {

index.html

@@ -36,6 +36,9 @@
     <button id="export-session" class="chat-toggle-btn" aria-label="Export session as markdown" title="Export session log as Markdown">
       📥
     </button>
+    <button id="podcast-toggle" class="chat-toggle-btn" aria-label="Start podcast of SOUL.md" title="Play SOUL.md as audio">
+      🎧
+    </button>
     <button id="podcast-toggle" class="chat-toggle-btn" aria-label="Start podcast of SOUL.md" title="Play SOUL.md as audio podcast">
       🎧
     </button>

style.css

@@ -109,6 +109,11 @@ canvas {
   font-family: var(--font-body);
   transition: background-color 0.2s ease;
 }
+
+#podcast-toggle:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}
 #podcast-toggle:hover {
   background-color: var(--color-primary);
 }