Improve tests, downloader, and project config

- Expand blender_downloader with better error handling and platform support
- Add test_main.py for main module tests
- Expand test coverage for introspect and generate_stubs
- Remove reportUnknownMemberType suppression from conformance config
- Exclude conformance/ from ruff linting (docs examples have E402)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

main.py

@@ -483,7 +483,6 @@ def conformance_check(versions: list[str] | None = None) -> None:
                     "typeCheckingMode": "strict",
                     "pythonVersion": python_version,
                     "reportUnusedExpression": False,
-                    "reportUnknownMemberType": False,
                 }
             )
         )