Merge path-level OpenAPI parameters

[kriptoburak]

Summary

• merge OpenAPI path-item parameters into each generated operation
• keep operation-level parameters authoritative when they share the same in and name
• add a generator test for a shared path parameter

Validation

• pytest tests/unit/test_generator.py -q

Notes

• pytest tests/unit -q currently reports 125 passed and 2 unrelated failures while importing mockloop_mcp.main: FastMCP.__init__() rejects the existing description argument with the installed MCP dependency.