Three QSS issues caused headings to render with only the top ~60%
visible:
- QGroupBox: margin-top 12px was insufficient for the title rendered
in subcontrol-origin: margin. Increased to 16px and added 2px
vertical padding to the title.
- QDockWidget::title: min-height 18px conflicted with padding 8px 6px,
constraining the content area. Removed min-height to let Qt auto-size
from padding + font metrics.
- QSint--ActionGroup QToolButton: min-height 18px forced a height that
was then clipped by the C++ setFixedHeight(headerSize) calculation.
Set min-height to 0px so the C++ layout controls sizing.
Closes#325
