Fixes#3256
When initiating an outbound call with an intro message (e.g., "Henrik asked
me to call about your mother"), the AI now receives this as explicit context
in its system prompt under "Purpose of this call".
Previously, the intro was played via TTS but the AI didn't understand the
call's objective, leading to generic follow-up questions instead of staying
on topic.
Changes:
- manager.ts: Store callPurpose in metadata at call creation time
- response-generator.ts: Accept callPurpose param and include in system prompt
- webhook.ts: Pass callPurpose to generateVoiceResponse
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>