When a user mentions a repository in room chat, extract the repo name
from @[repo:name:label] brackets, look up the full repo model from the
database, and inject its details (name, description, default branch,
visibility) into the AI message context. Works independently of
embed_service availability.
- Save thinking_content as {"__chunks__": [{type, content}]} for replay
- Tool call sanitization — don't expose raw results to frontend
- Billing record_ai_usage integration
- Room service module refactoring into service/ directory