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