fix(12.2-05): mark a partly filled time-mode datepicker invalid

The partial-segment check read only DateField segments, so a time-mode
field (Reka TimeField, data-reka-time-field-segment) with some segments
typed was never flagged. Read both segment attributes. DatepickerField
tests cover both UI-SPEC backstops (Escape focus and disabled days, the
fixed-zone datetime round trip) and the partly filled time case.

admin/src/components/form/fields/DatepickerField.vue

@@ -98,10 +98,11 @@ function refreshPartial(): void {
     return
   }
   // Only the editable number segments count: literals, the zone name, the
-  // day period and the calendar trigger carry the same data attribute.
-  const segments = Array.from(root.querySelectorAll<HTMLElement>('[data-reka-date-field-segment]')).filter((el) =>
-    NUMBER_PARTS.has(el.dataset.rekaDateFieldSegment ?? ''),
-  )
+  // day period and the calendar trigger carry the same data attribute. A
+  // date or datetime renders DateField segments, time mode TimeField ones.
+  const segments = Array.from(
+    root.querySelectorAll<HTMLElement>('[data-reka-date-field-segment], [data-reka-time-field-segment]'),
+  ).filter((el) => NUMBER_PARTS.has(el.dataset.rekaDateFieldSegment ?? el.dataset.rekaTimeFieldSegment ?? ''))
   const filled = segments.filter((el) => !el.hasAttribute('data-placeholder')).length
   partial.value = filled > 0 && filled < segments.length
 }