fix(traffic): date the STALE row by the oldest cached tile; add zh-Hant string

src/ui/layerPanel.test.mjs

@@ -93,6 +93,27 @@ test('partial feed controls distinguish incomplete records from stale data and o
   assert.equal(button.textContent, 'OFF');
 });
 
+test('a stale row dates cached data by its oldest tile, not the last load', async () => {
+  const { LayerPanel } = await import('./layerPanel.js');
+  const panel = LayerPanel.prototype;
+  const layer = {
+    id: 'traffic',
+    name: 'Street Traffic',
+    source: 'TomTom',
+    enabled: true,
+    stats: {
+      mode: 'live',
+      stale: true,
+      count: 4,
+      lastUpdate: Date.now(),
+      oldestTileAt: Date.now() - 3 * 3600_000,
+    },
+  };
+  assert.match(panel._buildMetaText(layer), /^STALE · TomTom · 3h ago$/);
+  delete layer.stats.oldestTileAt;
+  assert.match(panel._buildMetaText(layer), /^STALE · TomTom · just now$/);
+});
+
 test('readout rows contain only toggles and metadata; ordinary rows retain controls', async () => {
   const { LayerPanel } = await import('./layerPanel.js');
   const { railFixture } = await import('./railTestFixture.mjs');