fix: bound DUUL MCP review latency

[Suprhimp]

Summary

• cap each MCP review at 75 seconds and return structured timeout fallbacks
• reduce default reviewer exploration to three rounds, with bounded environment overrides
• add opt-in file diagnostics via DUUL_LOG_FILE

Investigation

• the current trenton session's last completed plan review was logged at 14:20; its subsequent submission never reached DUUL.

Validation

• npm test (96 tests passed)