* chore: bump minimum Python from 3.8 to 3.9 and adopt PEP 585 builtins
- Update requires-python, classifiers, mypy target, and black target in pyproject.toml
- Replace Python 3.8 with 3.9 in CI matrix and nightly workflow
- Replace typing.List/Dict/Tuple/Set with builtin list/dict/tuple/set (PEP 585)
- Update all 3.8 version references in README, docs, website, and install.sh
- Fix test_wayland_no_tools to mock IBus availability
- Remove List from common_types re-exports and update test
* style: reformat test files for Black 26.x and pin version in CI
Black 26.x introduced parenthesized context manager formatting.
Reformat 7 test files and pin Black>=26,<27 in CI to prevent
future drift from unpinned version upgrades.
