Remove the superseded headline-tiles computed

`tiles` built four stat objects that nothing rendered. The commit which cloned
DX-life's region dashboard replaced its template block with `stats` and the
shared StatCard, and removed the .rd-tile styles with it, but left the computed
behind.

It was not merely unused: it carried four bare English labels, so a localisation
scan reports it as hardcoded English every time. It cost this audit the time to
prove it harmless, and would have cost the next one the same. `stats` renders
the same four figures and puts every label through t().

Verified superseded rather than unfinished before deleting: the template usage
and the computed were added by one commit and the usage removed by the next, the
styles are already gone, and nothing in the plugin refers to it. Behaviour is
unchanged.

plugin-designs/regions-dashboard/region-dashboards.vue

@@ -234,18 +234,6 @@ const subject = computed(() => {
   return { kind: 'all', title: t('All Regions'), context: `${formatNumber(regions.value.length)} regions`, stats: all }
 })
 
-// Headline tiles. Every one of these is a COUNT the rollup actually measured — no ratio is
-// invented here that tab 1 could not also produce from the same records.
-const tiles = computed(() => {
-  const s = subject.value.stats || emptyStats()
-  return [
-    { label: 'People groups', value: formatNumber(s.count) },
-    { label: 'Population', value: formatNumber(s.population) },
-    { label: 'Engaged', value: formatNumber(s.engaged) },
-    { label: 'With prayer cover', value: formatNumber(s.withPrayer) },
-  ]
-})
-
 // ★ NO BAR CHART. It was ours, not theirs, and the rule is that a SELECTED region or country
 // must look IDENTICAL to its DX-life page — RegionDetail.vue has four stat cards, the map, three
 // goal cards and the country table, and nothing else. The one deliberate difference in this