DisplayMixin in _display.py takes the methods that reach widgets only through
self._widgets: apply, _play, _verdict, on_undo, on_quit, drain, refresh, tick
and attach_player.
Widget construction stays in ui.py on purpose. test_ui.py fakes the toolkit
with patch.object(ui, "tk", fake), so moving _build out makes 22 tests error
with "module ui does not have the attribute 'tk'". An earlier attempt did that
and was reverted rather than touching the tests.
Also dropped the four _key_* adapters; each only discarded Tk's event argument
before forwarding, so _bind_keys binds lambdas directly now.
One thing worth knowing for the next split: ruff's TC001 is NOT suppressed by
__all__ the way F401 is. Moving Callbacks to its own module and re-exporting it
left a TYPE_CHECKING-only import that lints clean and raises AttributeError at
runtime -- cli.py constructs ui.Callbacks. Reverted; it stays defined in ui.py.
ui.py 398 -> 242, _display.py 179. 277 tests pass, both files 100% covered.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011w2Pj4Ek3ZNMQVYcFHgXDY
