preserve xterm viewport intent when switching terminal tabs so
bottom-pinned sessions stay pinned and manually scrolled sessions
keep their history position
unify viewport restoration across activation, fit, and resize
paths to avoid losing scroll state after terminal reflow
Replace remaining hardcoded button and hover colors in
QuickCommandsView with existing theme utility classes.
This keeps add, empty-state, and item action buttons visually
consistent across themes without changing quick command behavior.
yinjianm