feat(optimizer): skill-aware reflection (EmbodiSkill S_app), config-controlled and env-independent

Split failure reflections into SKILL_DEFECT (body edit) vs EXECUTION_LAPSE
(protected appendix note that re-emphasizes an existing rule, never edited
by step-level analysts). Toggle: optimizer.use_skill_aware_reflection
(default false; baseline byte-identical when off).

- optimizer/appendix.py: protected APPENDIX region (inject/extract/append
  with dedup), mirrors the slow_update protected-field pattern
- optimizer/skill_aware.py: analyst prompt augmentation, appendix_notes
  parsing, threshold-gated LLM consolidation, and a process-wide runtime
  switch (configure_skill_aware_reflection) set once by the trainer
- gradient/reflect.py: augment error/success analyst prompts at runtime;
  None-sentinel kwargs resolve from the global switch, so env adapters
  need no per-benchmark wiring (works for all envs, present and future)
- optimizer/skill.py: generalize the protected-region check to
  (slow_update, appendix); edits inside any protected region are skipped
- engine/trainer.py: inject appendix at init, flush per-step
  EXECUTION_LAPSE notes after the gate settles, optional consolidation
- tests: regression suite incl. toggle-off byte-identical guarantee and
  env-independent global-switch resolution (6/6 passing + live smoke)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

skillopt/config.py

@@ -119,6 +119,9 @@ _FLATTEN_MAP: dict[str, str] = {
     "optimizer.slow_update_gate_with_selection": "slow_update_gate_with_selection",
     "optimizer.longitudinal_pair_policy": "longitudinal_pair_policy",
     "optimizer.use_meta_skill": "use_meta_skill",
+    "optimizer.use_skill_aware_reflection": "use_skill_aware_reflection",
+    "optimizer.skill_aware_appendix_source": "skill_aware_appendix_source",
+    "optimizer.skill_aware_consolidate_threshold": "skill_aware_consolidate_threshold",
     "evaluation.use_gate": "use_gate",
     "evaluation.gate_metric": "gate_metric",
     "evaluation.gate_mixed_weight": "gate_mixed_weight",