Add persona system for specialized review roles. Each persona defines:
- A specific review focus (security, architecture, documentation)
- Custom system prompt additions
- Personality/tone adjustments
Built-in personas: security, architect, docs
Custom personas: load from JSON via persona-file flag
Includes workspace validation to prevent path traversal attacks.
Closes#51
Explains the edit-in-place approach, state transition rules, worst-wins
escalation, and inline comment lifecycle. Includes a Mermaid state
diagram for visual reference.
Rodin