Fix: load operation validator extension in worker process (#280)

The worker was not loading the OperationValidatorExtension, so
operation validation was silently skipped for all async operations
(e.g. refresh_mental_model triggered after consolidation). The API
server already loaded this extension but the worker entry point was
missing it.

hindsight-api/hindsight_api/worker/main.py

@@ -176,7 +176,7 @@ def main():
         nonlocal memory, poller
         import uvicorn
 
-        from ..extensions import TenantExtension, load_extension
+        from ..extensions import OperationValidatorExtension, TenantExtension, load_extension
 
         # Load tenant extension BEFORE creating MemoryEngine so it can
         # set correct schema context during task execution. Without this,
@@ -184,6 +184,12 @@ def main():
         # causing worker writes to land in the wrong schema.
         tenant_extension = load_extension("TENANT", TenantExtension)
 
+        # Load operation validator so workers can record usage metering
+        # for async operations (e.g. refresh_mental_model after consolidation)
+        operation_validator = load_extension("OPERATION_VALIDATOR", OperationValidatorExtension)
+        if operation_validator:
+            logger.info(f"Loaded operation validator: {operation_validator.__class__.__name__}")
+
         # Initialize MemoryEngine
         # Workers use SyncTaskBackend because they execute tasks directly,
         # they don't need to store tasks (they poll from DB)
@@ -191,6 +197,7 @@ def main():
             run_migrations=False,  # Workers don't run migrations
             task_backend=SyncTaskBackend(),
             tenant_extension=tenant_extension,
+            operation_validator=operation_validator,
         )
 
         await memory.initialize()