Python: fix(claude): preserve $defs in JSON schema for nested Pydantic models (#3655)

* fix(claude): preserve $defs in JSON schema for nested Pydantic models

- Preserve $defs section from Pydantic JSON schema when converting FunctionTool to SDK MCP tool
- This fixes tools with nested Pydantic models that use $ref references
- Add test for nested type schema preservation

Fixes #3654

* Adjust shared state import

* Fix MCP tool kwargs serialization bug

---------

Co-authored-by: Evan Mattson <evan.mattson@microsoft.com>

python/packages/core/tests/workflow/test_edge.py

@@ -10,7 +10,6 @@ from agent_framework import (
     Executor,
     InProcRunnerContext,
     Message,
-    SharedState,
     WorkflowContext,
     handler,
 )
@@ -24,6 +23,7 @@ from agent_framework._workflows._edge import (
     SwitchCaseEdgeGroupDefault,
 )
 from agent_framework._workflows._edge_runner import create_edge_runner
+from agent_framework._workflows._shared_state import SharedState
 from agent_framework.observability import EdgeGroupDeliveryStatus
 
 # Add for test

python/packages/core/tests/workflow/test_workflow_states.py

@@ -8,7 +8,6 @@ from agent_framework import (
     ExecutorFailedEvent,
     InProcRunnerContext,
     RequestInfoEvent,
-    SharedState,
     Workflow,
     WorkflowBuilder,
     WorkflowContext,
@@ -20,6 +19,7 @@ from agent_framework import (
     WorkflowStatusEvent,
     handler,
 )
+from agent_framework._workflows._shared_state import SharedState
 
 
 class FailingExecutor(Executor):