Extract three cohesive modules from the monolithic lib.rs (3188 -> 2785 lines):
- metrics.rs (147 lines): Turn metrics tracking and histogram generation
- TurnMetrics struct
- format_elapsed_time() for human-readable durations
- generate_turn_histogram() for performance visualization
- Added unit tests for core functions
- project_files.rs (181 lines): Project file reading utilities
- read_agents_config() for AGENTS.md loading
- read_project_readme() for README detection
- read_project_memory() for .g3/memory.md
- extract_readme_heading() for display
- Added unit tests
- coach_feedback.rs (129 lines): Coach feedback extraction from session logs
- extract_from_logs() main entry point
- Helper functions for log parsing and text extraction
All modules have clear single responsibilities, improved documentation,
and maintain identical behavior to the original inline functions.
Agent: carmack
