Consolidate API and integration test files

- Merge test_api_compatibility.py + test_feature_matrix.py → test_api_surface.py
  Combines public export tests, C function mapping, and method signature tests
- Delete test_server_compatibility.py (covered by test_native_all_methods.py
  and test_behavioral_compatibility.py)

Test suite reduced from 574 to 424 tests while maintaining full coverage.
Files reduced from 13 to 11 test files.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: gijzelaerr