- test_deck_stack_exists: _deck_stack present; default shows _control_deck.
- test_pinning_two_panels_switches_to_split: pin 2 panels + refresh →
stack shows _deck_split_container.
Pin via _pinned flags directly (not the toggle handler) so no QSettings
write leaks into other function-scoped windows; existing 6 tests run in
default/tabbed state and still pass.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Ethanfel