fix(date-range-filter): drop text selection on arrow navigation

Arrow Left/Right called target.select(), which painted the segment with
the browser's default text-selection color instead of the brand focus
background used everywhere else — so a part looked pink when reached by
arrow keys but blue when clicked or tabbed into. The select() was
redundant (the digit handler already restarts a full part on the next
keypress), so removing it makes the focus highlight consistent.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ts/elements/date-range-picker.ts

@@ -290,7 +290,6 @@ function initField(picker: HTMLElement, calendarState: CalendarState): void {
         const target = segments[segmentIndex + step];
         if (target) {
           target.focus();
-          target.select();
         }
         return;
       }