Make catalog feed configuration optional and explicit

src/ui/layerPanel.js

@@ -588,7 +588,12 @@ export class LayerPanel {
   }
 
   _syncToggleButton(button, layer) {
-    const feedState = layer.enabled ? layerFeedState(layer.stats) : 'off';
+    const unavailable = layer.stats?.sourceUnavailable === true;
+    const feedState = unavailable
+      ? 'unavailable'
+      : layer.enabled
+        ? layerFeedState(layer.stats)
+        : 'off';
     const transitioning =
       layer.lifecycleState === 'enabling' ||
       layer.lifecycleState === 'disabling';
@@ -601,7 +606,7 @@ export class LayerPanel {
     for (const state of Object.keys(FEED_STATE_LABELS)) {
       button.classList.toggle(
         `feed-${state}`,
-        layer.enabled && !uncertain && feedState === state,
+        (layer.enabled || unavailable) && !uncertain && feedState === state,
       );
     }
     button.dataset.feedState = transitioning
@@ -613,16 +618,21 @@ export class LayerPanel {
     // click guard above prevents repeat activation without the focus loss caused
     // by native `disabled`.
     button.disabled = false;
-    button.setAttribute('aria-disabled', String(transitioning));
+    button.setAttribute(
+      'aria-disabled',
+      String(transitioning || (unavailable && !layer.enabled)),
+    );
     button.setAttribute('aria-busy', String(transitioning));
     button.textContent = transitioning
       ? layer.lifecycleState.toUpperCase()
       : uncertain
         ? 'UNCERTAIN'
-        : layer.enabled
+        : layer.enabled || unavailable
           ? FEED_STATE_LABELS[feedState]
           : 'OFF';
-    const keyGuidance = layerKeyRequirementTooltip(layer);
+    const keyGuidance = unavailable
+      ? String(layer.stats.error || 'Data source unavailable')
+      : layerKeyRequirementTooltip(layer);
     // Name the missing key on the control itself: a row reading KEY REQUIRED
     // without saying WHICH key leaves a dead control and no next step. Empty
     // when the layer needs no key, or already has one.

src/ui/layerPanel.test.mjs

@@ -228,3 +228,33 @@ test('the Recent Imagery readout mounts in its rail body like the weather readou
     globalThis.document = previousDocument;
   }
 });
+
+test('an omitted source is visibly unavailable and cannot be toggled on', async () => {
+  const { LayerPanel } = await import('./layerPanel.js');
+  const attrs = new Map();
+  const button = {
+    classList: { toggle() {} },
+    dataset: {},
+    setAttribute: (key, value) => attrs.set(key, value),
+  };
+  const layer = {
+    id: 'flights',
+    name: 'Flights',
+    enabled: false,
+    stats: {
+      sourceUnavailable: true,
+      status: 'unavailable',
+      error: 'Data source not configured: flights',
+    },
+  };
+  LayerPanel.prototype._syncToggleButton(button, layer);
+  assert.equal(button.textContent, 'UNAVAILABLE');
+  assert.equal(attrs.get('aria-disabled'), 'true');
+  assert.match(button.title, /not configured/);
+  LayerPanel.prototype._syncToggleButton(button, { ...layer, enabled: true });
+  assert.equal(
+    attrs.get('aria-disabled'),
+    'false',
+    'an active layer can always be switched off',
+  );
+});