Implements #60.
- Add ParsePersonaBytes() for parsing personas from byte data
- Add LoadRepoPersonas() to fetch personas from repo via Gitea API
- Add MergePersonas() to combine built-in and repo personas
- Add GetBuiltinPersonasMap() helper
- Update main.go to load repo personas first, fall back to built-in
- Add giteaClientAdapter to bridge gitea.Client to review.GiteaClient
When --persona is specified, the bot now:
1. Attempts to fetch personas from .review-bot/personas/*.yaml
2. If the named persona exists in the repo, uses it
3. Otherwise falls back to built-in personas
This allows repos to define domain-specific personas (e.g., trading
experts for gargoyle, crypto experts for kms-lite) without modifying
the review-bot codebase.
Rodin