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>

pyproject.toml

@@ -33,7 +33,7 @@ extraPaths = ["stubs"]
 exclude = ["downloads/", ".venv/", "dist/", "conformance/"]
 
 [tool.ruff]
-exclude = ["dist/"]
+exclude = ["dist/", "conformance/"]
 
 [tool.poe.tasks]
 format = { cmd = "black .", help = "Format all Python files" }