Update and reduce documentation files

[NiceAndPeter]

Cleaned up documentation directory by removing 29 outdated files:

• Removed ancient phase-specific docs (phases 2, 36, 115)
• Removed completed planning documents (constructors, encapsulation, LuaStack, macros)
• Removed duplicate files (docs/claude.md, STATUS_UPDATE, ROADMAP)
• Removed outdated analyses (lvm, lambda, loops, allocators, unions)

Updated remaining files:

• SPAN_MODERNIZATION_PLAN.md: Added Phase 115-116 status update
• TYPE_MODERNIZATION_ANALYSIS.md: Updated to reflect Phases 114-119 completion

Result:

• Before: 38 files, 25,043 lines
• After: 10 files, 8,280 lines
• Reduction: 67% fewer files, 67% fewer lines

Remaining essential documentation:

• CMAKE_BUILD.md (87 lines)
• COVERAGE_ANALYSIS.md (374 lines)
• REFACTORING_SUMMARY.md (452 lines)
• CPP_MODERNIZATION_ANALYSIS.md (953 lines)
• TYPE_MODERNIZATION_ANALYSIS.md (953 lines)
• GC_PITFALLS_ANALYSIS.md (995 lines)
• GC_SIMPLIFICATION_ANALYSIS.md (1,008 lines)
• SRP_ANALYSIS.md (1,008 lines)
• UNDEFINED_BEHAVIOR_ANALYSIS.md (1,179 lines)
• SPAN_MODERNIZATION_PLAN.md (1,271 lines)

All remaining docs are actively referenced in CLAUDE.md's Documentation Index.