refactor: add ToolConfig pydantic model, replace tool_config dicts

refactor: eliminate all Serializer classes, use Pydantic model_dump() directly

refactor: typed Pydantic config + Pydantic result models, eliminate dict access

feat(cam): add CAMPlan Pydantic model for structured output

feat(cam): add generate_gcode function with ocp-freecad-cam wrapper

feat(cam): add CAMResult dataclass and serializer