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/plugins/llm_analysis/plugin.py

@@ -1,12 +1,14 @@
-# #region backend/src/plugins/llm_analysis/plugin.py [C:3] [TYPE Module] [SEMANTICS plugin, llm, analysis, documentation]
+# [DEF:backend/src/plugins/llm_analysis/plugin.py:Module]
+# @COMPLEXITY: 3
+# @SEMANTICS: plugin, llm, analysis, documentation
 # @BRIEF Implements DashboardValidationPlugin and DocumentationPlugin.
-# @LAYER Domain
-# @INVARIANT All LLM interactions must be executed as asynchronous tasks.
+# @LAYER: Domain
 # @RELATION INHERITS -> [PluginBase]
 # @RELATION CALLS -> [ScreenshotService]
 # @RELATION CALLS -> [LLMClient]
 # @RELATION CALLS -> [LLMProviderService]
-# @RELATION USES -> [TaskContext]
+# @RELATION USES -> TaskContext
+# @INVARIANT: All LLM interactions must be executed as asynchronous tasks.
 
 from typing import Dict, Any, Optional
 import os
@@ -31,8 +33,8 @@ from ...services.llm_prompt_templates import (
 
 # #region _is_masked_or_invalid_api_key [TYPE Function]
 # @BRIEF Guards against placeholder or malformed API keys in runtime.
-# @PRE value may be None.
-# @POST Returns True when value cannot be used for authenticated provider calls.
+# @PRE: value may be None.
+# @POST: Returns True when value cannot be used for authenticated provider calls.
 def _is_masked_or_invalid_api_key(value: Optional[str]) -> bool:
     key = (value or "").strip()
     if not key:
@@ -45,8 +47,8 @@ def _is_masked_or_invalid_api_key(value: Optional[str]) -> bool:
 
 # #region _json_safe_value [TYPE Function]
 # @BRIEF Recursively normalize payload values for JSON serialization.
-# @PRE value may be nested dict/list with datetime values.
-# @POST datetime values are converted to ISO strings.
+# @PRE: value may be nested dict/list with datetime values.
+# @POST: datetime values are converted to ISO strings.
 def _json_safe_value(value: Any):
     if isinstance(value, datetime):
         return value.isoformat()
@@ -59,7 +61,7 @@ def _json_safe_value(value: Any):
 
 # #region DashboardValidationPlugin [TYPE Class]
 # @BRIEF Plugin for automated dashboard health analysis using LLMs.
-# @RELATION IMPLEMENTS -> [backend.src.core.plugin_base.PluginBase]
+# @RELATION IMPLEMENTS -> backend.src.core.plugin_base.PluginBase
 class DashboardValidationPlugin(PluginBase):
     @property
     def id(self) -> str:
@@ -88,8 +90,8 @@ class DashboardValidationPlugin(PluginBase):
             "required": ["dashboard_id", "environment_id", "provider_id"]
         }
 
-    # #region DashboardValidationPlugin.execute [TYPE Function]
-    # @BRIEF Executes the dashboard validation task with TaskContext support.
+    # [DEF:DashboardValidationPlugin.execute:Function]
+    # @PURPOSE: Executes the dashboard validation task with TaskContext support.
     # @PARAM: params (Dict[str, Any]) - Validation parameters.
     # @PARAM: context (Optional[TaskContext]) - Task context for logging with source attribution.
     # @PRE: params contains dashboard_id, environment_id, and provider_id.
@@ -317,12 +319,12 @@ class DashboardValidationPlugin(PluginBase):
 
             finally:
                 db.close()
-    # #endregion DashboardValidationPlugin.execute
+    # [/DEF:DashboardValidationPlugin.execute:Function]
 # #endregion DashboardValidationPlugin
 
 # #region DocumentationPlugin [TYPE Class]
 # @BRIEF Plugin for automated dataset documentation using LLMs.
-# @RELATION IMPLEMENTS -> [backend.src.core.plugin_base.PluginBase]
+# @RELATION IMPLEMENTS -> backend.src.core.plugin_base.PluginBase
 class DocumentationPlugin(PluginBase):
     @property
     def id(self) -> str:
@@ -351,8 +353,8 @@ class DocumentationPlugin(PluginBase):
             "required": ["dataset_id", "environment_id", "provider_id"]
         }
 
-    # #region DocumentationPlugin.execute [TYPE Function]
-    # @BRIEF Executes the dataset documentation task with TaskContext support.
+    # [DEF:DocumentationPlugin.execute:Function]
+    # @PURPOSE: Executes the dataset documentation task with TaskContext support.
     # @PARAM: params (Dict[str, Any]) - Documentation parameters.
     # @PARAM: context (Optional[TaskContext]) - Task context for logging with source attribution.
     # @PRE: params contains dataset_id, environment_id, and provider_id.
@@ -473,7 +475,7 @@ class DocumentationPlugin(PluginBase):
 
             finally:
                 db.close()
-    # #endregion DocumentationPlugin.execute
+    # [/DEF:DocumentationPlugin.execute:Function]
 # #endregion DocumentationPlugin
 
-# #endregion backend/src/plugins/llm_analysis/plugin.py
+# [/DEF:backend/src/plugins/llm_analysis/plugin.py:Module]