Keep the news layer inside its day and its memory bounds

From review of the news layer:
- An event's other sides older than 24 hours (or undated) are no longer
  listed, and a report dated more than 15 minutes ahead is outside the
  window, as in the regional brief.
- Picture cards are one canvas per event in a bounded cache (24), repainted
  in place when the age changes, with each card's picture dropped with it;
  the age in the key had made a new canvas every minute.
- The feed list drops reports that leave the window and is capped at 600.
- "In view" is filtered from the reports the layer already holds; it reads
  the feed only with minor news on, once per refresh, never per pan.
- Infinite scroll restarts after a filter change or a failed read.
- The two filter selects stack, so "Significant and above" is not cut off.
- The timeout tests hold the event loop until aborted, so they pass on
  Node 22 as well.

server/providers/news.test.mjs

@@ -124,10 +124,16 @@ test('upstream failures, bad JSON and timeouts become bounded errors', async ()
   const slow = mount({
     origin: () => 'https://news.example',
     timeoutMs: 10,
+    // AbortSignal.timeout does not hold the event loop open: the hanging
+    // fetch does, until its signal aborts, so the run cannot end before it.
     fetchImpl: (_url, { signal }) =>
-      new Promise((_, reject) =>
-        signal.addEventListener('abort', () => reject(signal.reason)),
-      ),
+      new Promise((_, reject) => {
+        const alive = setTimeout(() => {}, 60_000);
+        signal.addEventListener('abort', () => {
+          clearTimeout(alive);
+          reject(signal.reason);
+        });
+      }),
   });
   const timedOut = await slow('/hotspots');
   assert.equal(timedOut.status, 504);