Ask a natural-language question about a GitHub repository and get an answer grounded in the real code. READ-ONLY: never writes, edits, builds, or executes anything. The harness fetches the repo itself (clone or refresh, max every few days) — a nonexistent repo fails fast with the exact git error. Stateful PER REPOSITORY: continue_session=true resumes the latest discussion of that owner/repo (follow-up questions keep their context); false (default) starts a fresh one. Optional branch pins a specific branch. Use it for architecture questions, where a feature lives, request flow, conventions, design rationale, etc.