Add Astral's ty type checker (written in Rust, 10-100x faster than mypy)
as a second type checking layer. Both run in pre-commit and CI.
Fixed type issues caught by ty:
- config.py: explicit Host constructor to avoid dict unpacking issues
- executor.py: wrap subprocess.run in closure for asyncio.to_thread
- api.py: use getattr for Jinja TemplateModule macro access
- test files: fix playwright driver_path tuple handling, pytest rootpath typing
