Phase 112: Optimize loop variable types for type safety

Improvements:
1. ltable.cpp:999 - Safer unsigned decrement pattern in hash table search
   - Changed from `while (i--)` to `while (i > 0) { i--; }`
   - Prevents potential wraparound issues if nodeSize() returns 0
   - More explicit loop termination condition

2. funcstate.cpp:238 - Explicit static_cast in variable search
   - Extract loop count before loop initialization
   - Use static_cast<int> instead of cast_int macro
   - Improves code clarity and modern C++ style

Documentation:
- Added comprehensive loop analysis (docs/LOOP_OPTIMIZATION_ANALYSIS.md)
- Analyzed 45+ loop patterns across hot-path files
- Identified type safety improvements and modernization opportunities

Performance:
- Baseline: 4.60s average (range 4.33-4.87s)
- With optimizations: 4.54s average (range 4.24-4.82s)
- Result: 1.3% improvement, well within 3% tolerance

Testing:
- All tests passing ("final OK !!!")
- Zero warnings with -Werror
- Type safety improvements with no performance regression

Author: claude