docs: PHASE_HISTORY v1.4 + CAPABILITY_MATRIX regen for Phase 13.16.DF FIX1

PHASE_HISTORY.md (v1.4):
  - Add Phase 13.16.DF FIX1 retrospective entry
  - Update header status: 451 -> 469 tests, 43 -> 46 features,
    21 -> 28 invariance tests, 6 -> 7 Verified
  - Statistics Summary: new row (469, +18); totals -> 16 phases
  - Lessons Learned: +4 'What Worked Well', +2 'What Could Improve'
  - Best Practices: +4 (forwarded-name tuples, AST-derived inventories,
    scope-positive divergence pattern, three-level test coverage)
  - Revision History: v1.4 entry
  - 5-iteration source-verification chain documented
    (symptom -> location -> documentation -> runtime -> pipeline)
  - Cross-subproject end-to-end verification via Phase 13.19.ADF.FIX1

CAPABILITY_MATRIX.md:
  - Auto-regenerated by run_tests.sh after FIX1 commit fe007b7
  - Reflects post-FIX1 state: 46 features, 7 Verified, 39 Smoke-only,
    0 Broken, 28 invariance tests, 170 total proof tests
  - Known stale: header still says 'Phase: 13.15.DF' (script hardcodes it).
    Tracked as P1-CC-4 in PHASE_13_16_DF_FIX1_END_CODE_REVIEW_SUMMARY.
    Generator script fix planned as separate housekeeping commit
    (per scaffolding-separation rule, doc commits should not touch
    tooling).

Closes Phase 13.16.DF FIX1 documentation update.

Refs: PHASE_13_16_DF_FIX1_END_CODE_REVIEW_SUMMARY.md, items 4 + 6
      (recommended housekeeping)

Author: miranov25

UTILS/dfextensions/dfdraw/docs/CAPABILITY_MATRIX.md

@@ -1,6 +1,6 @@
 # Capability Matrix — dfdraw
 
-**Generated:** 2026-04-15 07:03 UTC
+**Generated:** 2026-04-15 07:10 UTC
 **Phase:** 13.15.DF
 **Generator:** `scripts/generate_capability_matrix.py`
 **Sources:** `tests/feature_taxonomy.py` + `tests/test_layer_classification.py`