Docs: PHASE_HISTORY v5.0 + TECHNICAL_SUMMARY v3.0

PHASE_HISTORY v5.0:
  Phases 13.10.GB through 13.15.GB documented
  COG deferral incident recorded
  Technical decisions table updated (14 new entries)
  Performance: 300× speedup for SW aggregation
  133 features, 500 tests, 43 Verified, 0 Broken

TECHNICAL_SUMMARY v3.0:
  New APIs: make_sliding_window_aggregate, make_nonlinear_sliding_window_fit
  Expression-based linear columns, sigma-clipped aggregation
  WLS fix, fit_intercept fix, lean output documented
  O2DistAI Q&A: selection, counts, weights, memory contracts
  Decision tree updated with 6 new entry points

Author: miranov25