Docs: PHASE_HISTORY.md v1.8 — append Phases 13.37 through 13.39 (2026-05-21 session)

Strictly append-only from v1.7 base (commit 2e5c83d). No existing line
removed or shortened. All pre-existing content preserved verbatim:
API Stability, Cross-Component Integration, Open Items, Lessons Learned,
Best Practices, Revision History entries 1.0-1.7 all intact.

New H2 phase sections (+4, inserted before Statistics Summary):
  - Phase 13.37.DF v1.1 (commit 67fccf3, 843→867, +24 tests)
    Histogram robustness: BUG-014 (step edgecolor sentinel), BUG-015
    (profile float group_by guard), BUG-016 (_interval_sort_key no-op
    for pd.Interval — verified by execution), hist_errors=True (Poisson
    error bars, 3-tier NaN/Σw² support), linestyle_cycle=True (Phase
    13.26 channels.cycles.linestyle). Sentinel extended to edgecolor +
    linestyle. Spec: 2 P0 rounds (v1.0→v1.1).

  - Phase 13.37.DF FIX1 (commit 095d6f2, 867→870, +3 tests)
  - Phase 13.37.DF. Phase 13.36 backward-compat locks. Promoted
    PROFILE.group_by_bins, SAME.auto_features, VECTOR.color_cycle from
    Smoke to Verifie    Smoke to Verifiebugs caught at code time: label
    filter anti-pattern (marker!='_' not label-based) + SO.COMPAT.3
    vector-vs-scala    vec premise (reformulated as vector-path
    invariance lock). Source    invariance lock). Source    invariance lmmit 0f52574, 870→889, +19 tests)
    Scatter enhancements. BUG-017 (facet_by f    Scatter enhancements. BUG-017 (facet_by f5 class, discovered via plot_kwargs scope). xerr=/yerr=
    error bars with _eval_error() helper (3-tier NaN policy: raise 100%
    / warn >50% / silent ≤50    / warn >50% / silent ≤50    / warn >50% / silent ≤P0-1 (column before to_rgba; regression-lock ECM.6).
    Expression marker= (boolean df    Expression marker= (boolean QRC
    v1.32 carry-forward: get_array() over get_facecolor() for colormap
    dispatch verification. Verified: 37→42, Invariance: 196→215.

  - Ph  - Ph  - Ph  - Ph  - Phts b024414 + 3c5d454, 889→913, +24 tests)
    2D Profile (profcolz): draw_profile2d() via z:y:x expression
    (colon_count==2 intercepted before _parse_expr); scipy.stats.
    binned_statistic_2d; min_entries= masking; pcolormesh + colorbar;
    ROOT TProfile2D equivalent. Time Axis: time_format= kwarg on 4 p    ROOT TProfile2D equivalent. Time Axis: time_format= kwarg on 4 p    ROOT TProfile2D equivaler3D: type='sc    ROOT TProfile2D equivalent. Time Axis: time_format= kwarg on 4 p    ROOT TProfile2D equivalent. Time Axis: time_format= kwarg on 4 p   e64 dty    ROOT TProfile2D equivalent. Time Axis: time_format= kwarelev/azim not in FORWARDED_NAMES).
    Verified: 42→47, Invariance: 215→239.

Statistics Summary: 4 new rows appended (13.37/37-FIX1/38/39);
  Total Development updated: 37→41 phase entries, 843→913 tests,
  90→105 features, 193→239 invariance tests, 33→47 Verified features.
Phase-ordering note added (post-13.36 monotonic commit sequence).

RevisioRevisioRevisioRevisioRevisioRevisioRevisioRevisioRevisioRev Status: updated to Phase 13.39.DF v1.2, tag PHASE_13_39_DF_END.

Sources: gitlog.txt (commits 2f4d959..3c5d454),
  CAPABILITY_MATRIX.md (47 Verified / 239 invariance / 913 tests),
  session approval summaries (Sonet50_PHASE_13_37/38/39_*_
  ReviewSummary_AllReviewers_20260521.md).

Author: miranov25