Add community results and ground COMPILATION_CACHING language in measured data

[AvdLee]

Summary

• Add Enchanted, Wikipedia iOS, and Kickstarter iOS to the community results table with links to their upstream PRs
• Replace vague COMPILATION_CACHING language across all skill docs with data-backed framing

Community Results

App	Clean Build	Incremental Build
Stock Analyzer	41.5s → 33.2s (-8.3s / 20% faster)	5.3s → 3.6s (-1.7s / 32% faster)
Enchanted	19.4s → 16.6s (-2.8s / 14% faster)	2.5s → 2.2s (-0.3s / 12% faster)
Wikipedia iOS	48.7s → 46.5s (-2.2s / 5% faster)	12.9s → 12.2s (-0.7s / 5% faster)
Kickstarter iOS	83.4s → 83.5s (~0s / within noise)	10.9s → 10.6s (-0.3s / 3% faster)

COMPILATION_CACHING language improvement

Before (across skill docs): "Impact on wait time is uncertain", "trust documented benefit", "the benefit is real but requires a different measurement approach"

After: "Measured 5-14% faster clean builds across tested projects (87 to 1,991 Swift files). The benefit compounds in real developer workflows where the cache persists between builds -- branch switching, pulling changes, and CI with persistent DerivedData."

Files updated: build-settings-best-practices.md, generate_optimization_report.py, orchestrator SKILL.md, fixer SKILL.md, orchestration report template.