logger: migrate belief_scope from legacy markers to molecular CoT protocol

Replace [Entry]/[Exit]/[Action]/[COHERENCE:OK] with [REASON]/[REFLECT]/[EXPLORE]
in belief_scope context manager, BeliefFormatter, and 34 source files.
Per molecular-cot-logging skill invariants.

backend/src/scripts/migrate_sqlite_to_postgres.py

@@ -165,7 +165,7 @@ def _migrate_config(engine, legacy_config_path: Optional[Path]) -> int:
     with belief_scope("_migrate_config"):
         if legacy_config_path is None:
             logger.info(
-                "[_migrate_config][Action] No legacy config.json found, skipping"
+                "[_migrate_config][REASON] No legacy config.json found, skipping"
             )
             return 0
 
@@ -328,7 +328,7 @@ def run_migration(
 ) -> Dict[str, int]:
     with belief_scope("run_migration"):
         logger.info(
-            "[run_migration][Entry] sqlite=%s target=%s", sqlite_path, target_url
+            "[run_migration][REASON] sqlite=%s target=%s", sqlite_path, target_url
         )
         if not sqlite_path.exists():
             raise FileNotFoundError(f"SQLite source not found: {sqlite_path}")

backend/src/scripts/seed_superset_load_test.py

@@ -382,7 +382,7 @@ def main() -> None:
         args = _parse_args()
         result = seed_superset_load_data(args)
         logger.info(
-            f"[COHERENCE:OK] Result summary: {json.dumps(result, ensure_ascii=True)}"
+            f"[REFLECT] Result summary: {json.dumps(result, ensure_ascii=True)}"
         )