fix: use realtimeInput.text for intro prompt, handle Blob WebSocket data

- Introduction prompt uses realtimeInput.text format (not clientContent)
- Agent now successfully introduces itself and sends audio responses
- Playback AudioContext created in user gesture for mobile

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/configurator/VoiceAgentProvider.tsx

@@ -339,9 +339,8 @@ export default function VoiceAgentProvider({ locale, children }: VoiceAgentProvi
           trackAmplitude();
           // Prompt the agent to introduce itself
           ws.send(JSON.stringify({
-            clientContent: {
+            realtimeInput: {
-              turns: [{ role: 'user', parts: [{ text: 'Hello, please introduce yourself.' }] }],
+              text: 'Hello, please introduce yourself.',
-              turnComplete: true,
             },
           }));
           return;