QRadioButton was unstyled, so the selected trigger option was invisible on the
dark theme. Added QRadioButton::indicator styling (accent ring + center dot when
checked) and explicit QCheckBox :checked/:disabled states. Bundle checkboxes stay
selectable even when already installed so the page isn't dead when all deps are
present.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>