semantics: complete DEF-to-region migration, fix regressions

- Convert legacy [DEF🆔Type] anchors to #region/#endregion across 329 files
- Reinstate _normalize_timestamp_value in sql_generator.py
- Fix MarkerLogger→logger migration in events.py (molecular CoT markers)
- Fix dataset_review orchestrator dependencies (_build_execution_snapshot)
- Fix config_manager stale-record deletion (moved to save path only)
- Add 77 missing [/DEF:] closers in 5 unbalanced test files
- Update assistant_chat.integration.test.js for #region format
- Apply molecular-cot-logging markers (REASON/REFLECT/EXPLORE) via logger.* methods

backend/src/services/git_service.py

@@ -1,10 +1,11 @@
-# #region git_service [C:1] [TYPE Module:Tombstone]
+# [DEF:git_service:Module:Tombstone]
+# @COMPLEXITY: 1
 # @BRIEF Re-export shim — GitService has been decomposed into services/git/ package.
 #           All consumers continue to import from this same path without changes.
-# @RELATION: REDIRECTS_TO -> [GitServiceModule]
+# @RELATION REDIRECTS_TO -> [GitServiceModule]
 # @RATIONALE: Monolithic GitService (2101 lines) was decomposed into 8 domain-specific mixins
 #             under services/git/ to satisfy INV_7 (< 400 lines per module). This shim preserves
 #             the original import path for all 5 consumers.
 # @REJECTED: Breaking 5 consumer imports to remove this shim — unacceptable migration cost.
 from src.services.git import GitService  # noqa: F401
-# #endregion git_service
+# [/DEF:git_service:Module:Tombstone]