Add comprehensive header/cpp file organization analysis

- Identified 3 oversized headers (lobject.h: 2,027 lines, lstate.h: 1,309 lines, lparser.h: 830 lines)
- Documented excellent patterns (VM split: 7 .cpp files, GC modularization: 6 modules)
- Proposed Phase 121: Header Modularization to address technical debt
- Expected impact: 20-40% compilation time improvement
- Detailed action plan with 14-hour effort estimate

Author: claude