fix(status): stop false LOAD FAILED from a relayed adsb.lol 429 and the installations zoom prompt

Two independent triggers turned the global status chip red while every layer
was still populated (reproduced at JFK in Cockpit; timeline in the issue).

adsb.lol proxy: a non-OK upstream status was relayed verbatim even with a
12 s-old cache in hand, and the browser layer answers a 429 with a 45 s
cooldown in which every refresh reports "adsb.lol rate limited" without a
network call. The proxy now serves its cached body as STALE on a 429/5xx and
backs off from upstream for Retry-After (bounded), mirroring the OpenSky
proxy. A failure with nothing cached is still relayed.

Mapped installations: the "zoom in" guidance was stored in `error`, so the
manager reported a refresh failure and the chip a LOAD FAILED whenever the
view could not be bounded (Cockpit looks at the horizon). The status is now
set without an error string; the row reads the prompt from `statusMessage`,
and the chip ignores `error` for guidance statuses, matching the carve-out
layerFeedState already has.

src/loadingFeedback.js

@@ -5,6 +5,8 @@ export const LOADING_TERMINAL_DWELL_MS = 2200;
 export const LOADING_FAILURE_DWELL_MS = 5000;
 export const LOADING_LONG_THRESHOLD_MS = 30000;
 export const TRAFFIC_SYNC_CONFIRM_MS = 1500;
+/** Layer statuses that are user guidance, not feed faults (see manager.js layerFeedState). */
+export const GUIDANCE_STATUSES = Object.freeze(['zoom-in', 'empty', 'idle']);
 
 function finiteCount(value) {
   const number = Number(value);
@@ -20,7 +22,13 @@ export function normalizeLayerLoading(layer = {}) {
   const loading = lifecycleState === 'enabling' || disabling || stats.loading === true || stats.refreshing === true;
   const count = finiteCount(stats.count);
   const stoppingInstallations = layer.id === 'military-installations' && disabling;
-  const error = stoppingInstallations ? null : stats.error || stats.lastError || stats.managerRefreshError || null;
+  // Guidance statuses ask the user to act (zoom in, run a search). They are
+  // normal operation, never a batch failure — mirrors layerFeedState's carve-out
+  // so a prompt stored alongside the status cannot turn the chip red.
+  const guidance = GUIDANCE_STATUSES.includes(status);
+  const error = stoppingInstallations || guidance
+    ? null
+    : stats.error || stats.lastError || stats.managerRefreshError || null;
   const unavailable = !stoppingInstallations && (stats.unavailable === true
     || stats.available === false
     || ['unavailable', 'offline', 'down', 'error'].includes(status));