Refreshing the widget directly from the setter raced when a setting was
flipped and flipped back quickly: two concurrent updateAll calls could
coalesce around a stale read and leave the widget on the intermediate value.
Observe the agenda-widget-range and week-start prefs instead and push a
single debounced updateAll once changes settle, so the widget always
converges to the final value.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>