fix: admit minimal Coffee Chat Bench contract

[openboa]

Outcome

Allow the central trusted Coffee gate to recognize the research-standard Coffee Chat Bench layout while continuing to accept the currently merged legacy skeleton during the transition.

Scope

• recognizes the three output-quality task directories and separate skill-triggering splits
• requires PREREGISTRATION.md but no speculative Data Card or case schema
• rejects incomplete and mixed legacy/current layouts
• keeps candidate repository policy code inert in the trusted zero-base path
• rejects candidate gitlinks before quality checks

Evidence

• npm test: 24/24 passing
• shell and Node syntax checks passing
• clean committed worktree at 4522494

Boundary

This changes protected central controls and must pass the existing coffee-security human gate. It does not activate a benchmark or establish Product performance.

Tracks openboa-ai/coffee-chat-bench#78.