Stop emitting LayoutUpdated for text-only menu label changes
Remove update_item() calls for label-only updates in _update_status(),
_update_sync(), and _update_live_stats(). Labels are still assigned to
MenuItem objects so KDE reads fresh values via GetLayout on menu open.
Only structural changes (pause/resume visibility toggles) now emit
LayoutUpdated, fixing the 5-second menu blink on KDE.