fix: clean up partial workers if start_processes fails in __enter__

Python skips __exit__ when __enter__ raises, so an exception mid-startup
would leak any workers already spawned. Wrap the call so stop_processes()
runs before the exception propagates.

Author: nthmost-orkes

src/conductor/client/automator/task_handler.py

@@ -329,7 +329,13 @@ def __init__(
         logger.info("TaskHandler initialized")
 
     def __enter__(self):
-        self.start_processes()
+        try:
+            self.start_processes()
+        except BaseException:
+            # __exit__ is not called if __enter__ raises, so clean up any
+            # partially-spawned workers here before propagating.
+            self.stop_processes()
+            raise
         return self
 
     def __exit__(self, exc_type, exc_value, traceback):