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/models/mapping.py

@@ -1,20 +1,18 @@
 # #region MappingModels [C:3] [TYPE Module] [SEMANTICS database, mapping, environment, migration, sqlalchemy, sqlite]
-# @BRIEF Defines the database schema for environment metadata and database mappings using SQLAlchemy.
-# @LAYER Domain
-# @INVARIANT All primary keys are UUID strings.
-# @RELATION DEPENDS_ON -> [sqlalchemy]
 #
+# @BRIEF Defines the database schema for environment metadata and database mappings using SQLAlchemy.
+# @LAYER:     Domain
+# @RELATION DEPENDS_ON -> sqlalchemy
 
 #
+# @INVARIANT: All primary keys are UUID strings.
 # @CONSTRAINT: source_env_id and target_env_id must be valid environment IDs.
 
-# [SECTION: IMPORTS]
 from sqlalchemy import Column, String, Boolean, DateTime, ForeignKey, Enum as SQLEnum
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.sql import func
 import uuid
 import enum
-# [/SECTION]
 
 Base = declarative_base()
 
@@ -39,7 +37,7 @@ class MigrationStatus(enum.Enum):
 
 # #region Environment [C:3] [TYPE Class]
 # @BRIEF Represents a Superset instance environment.
-# @RELATION DEPENDS_ON -> [MappingModels]
+# @RELATION DEPENDS_ON -> MappingModels
 class Environment(Base):
     __tablename__ = "environments"
 
@@ -80,7 +78,7 @@ class MigrationJob(Base):
 # #region ResourceMapping [C:3] [TYPE Class]
 # @BRIEF Maps a universal UUID for a resource to its actual ID on a specific environment.
 # @TEST_DATA: resource_mapping_record -> {'environment_id': 'prod-env-1', 'resource_type': 'chart', 'uuid': '123e4567-e89b-12d3-a456-426614174000', 'remote_integer_id': '42'}
-# @RELATION: DEPENDS_ON -> MappingModels
+# @RELATION DEPENDS_ON -> MappingModels
 class ResourceMapping(Base):
     __tablename__ = "resource_mappings"
 
@@ -94,3 +92,4 @@ class ResourceMapping(Base):
 # #endregion ResourceMapping
 
 # #endregion MappingModels
+