Reduce explanation length to 100 words max

Shorter explanations for quicker TTS and better pacing.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/agent.py

@@ -274,7 +274,7 @@ def run_agent(topic: str, persona_name: str, audience: str = "") -> Generator[di
 You are explaining a topic to someone. Your explanation should be:
 1. Entertaining and fully in character
 2. Educational - actually explain the concept clearly
-3. MAXIMUM 150 words - be concise!
+3. MAXIMUM 100 words - be concise!
 4. Natural spoken language (will be read aloud)
 5. Engaging and memorable{audience_context}