fix(debug): import debugpy lazily so workers don't require it

debug.py imported debugpy at module scope, so every Temporal worker
startup (run_worker.py imports setup_debug_if_enabled) required debugpy
to be installed. debugpy is a development-only tool and was only ever
satisfied transitively via ipykernel; agentex-sdk 0.11.5 dropped that
runtime dep, so worker startup began failing with "No module named
'debugpy'" and the temporal tutorials timed out waiting for the agent.

Move the import inside the AGENTEX_DEBUG_ENABLED branch where it's
actually used, so normal (non-debug) startup never needs debugpy.

Author: smoreinis

src/agentex/lib/utils/debug.py

@@ -6,8 +6,6 @@
 
 import os
 
-import debugpy  # type: ignore
-
 from agentex.lib.utils.logging import make_logger
 
 logger = make_logger(__name__)
@@ -30,6 +28,13 @@ def setup_debug_if_enabled() -> None:
         Any exception from debugpy setup (will bubble up naturally)
     """
     if os.getenv("AGENTEX_DEBUG_ENABLED") == "true":
+        # Imported lazily: debugpy is a development-only tool, so a normal
+        # worker startup must not require it to be installed.  Importing it at
+        # module scope forced it onto every worker (it used to be satisfied
+        # transitively via ipykernel; that dep was dropped in agentex-sdk
+        # 0.11.5, surfacing this as "No module named 'debugpy'").
+        import debugpy  # type: ignore
+
         debug_port = int(os.getenv("AGENTEX_DEBUG_PORT", "5678"))
         debug_type = os.getenv("AGENTEX_DEBUG_TYPE", "worker")
         wait_for_attach = os.getenv("AGENTEX_DEBUG_WAIT_FOR_ATTACH", "false").lower() == "true"