fix(cctv): space out failed background refreshes; test the stale paths

- A background catalog refresh that rejects now keeps the old catalog for
  another TTL, as an empty refresh already did, so a refresh that keeps
  failing is retried once per TTL instead of on every request.
- Trim notes are keyed by the source list they describe, and /sources asks
  for the list it served, so a request answered during a refresh never pairs
  the old cameras with the new list's notes.
- Tests: a failed background refresh (one warning, no unhandled rejection,
  no retry before the TTL, trim notes stay with their list) and an empty
  background refresh (old catalog kept, no upstream fetch before the TTL).
  The race assertion's message now names the failure; its timer is cleared.
- The Tarktee test no longer imports the new constant, so on main it fails
  on its own assertion instead of taking the whole file down.
- precompute-cctv-heights waits 60 s for a cold catalog, past Tarktee's 30 s.
- CURRENT-STATE notes the 30 s bound and the retry spacing.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

scripts/precompute-cctv-heights.mjs

@@ -326,8 +326,10 @@ async function main() {
       'src/data/local_data/cctv_ground_heights/cctv_ground_heights.json',
   );
   let sidecar = await loadSidecar(output);
+  // A cold catalog waits for its slowest pack (Tarktee gets 30 s), so allow
+  // more than that.
   const response = await fetch(`${base}/api/cctv/sources`, {
-    signal: AbortSignal.timeout(30_000),
+    signal: AbortSignal.timeout(60_000),
   });
   if (!response.ok) throw new Error(`Catalog HTTP ${response.status}`);
   const catalog = await response.json();