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/api/routes/git/__init__.py

@@ -1,6 +1,6 @@
 # #region GitPackage [C:3] [TYPE Module] [SEMANTICS git, package, re-exports]
 # @BRIEF Package root for decomposed git routes. Re-exports all public symbols from submodules.
-# @LAYER API
+# @LAYER: API
 # @RELATION USES -> [GitRouter, GitDeps, GitHelpers, GitConfigRoutes, GitGiteaRoutes,
 #                     GitRepoRoutes, GitRepoOperationsRoutes, GitRepoLifecycleRoutes,
 #                     GitMergeRoutes, GitEnvironmentRoutes]