Attention cues review fixes (#238)

- NEW lane: Gate A notice pinned below the rows (it scrolled off with >3
  entries, same rule as the rail, #46); rows at text-xs for the wall.
- Mobile chip moved off MapView's centred "Live" chip, which it covered.
- Keyword cues re-resolve to the incident once correlation links the call,
  so the lane row is clickable and the pin pulses.
- Enabling notifications sends one confirmation notification; a browser
  that grants permission but throws on construct (mobile Chrome) now shows
  "unsupported" instead of a switched-on control that never delivers.
- useActiveIncidentsState: includeMetadataChanges so `loaded` flips on a
  metadata-only server sync (quiet org / offline start) instead of waiting
  for the first incident change and swallowing it into the baseline.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/components/live/AttentionControls.tsx

@@ -173,6 +173,20 @@ export function AttentionControls({ prefs, onChange, armed }: Props) {
     if (p === "default") {
       try { p = (await Notification.requestPermission()) as NotifyState; } catch { p = notifyState(); }
     }
+    if (p === "granted") {
+      // Confirm with one notification (as the tone confirms with a beep). It
+      // doubles as the support check: mobile Chrome grants permission but
+      // throws on `new Notification()` without a service worker, which would
+      // otherwise leave a switched-on control that never delivers anything.
+      try {
+        new Notification("DRB · Notifications on", {
+          body: `Cues will appear here while the live wall tab is hidden.\n${MACHINE_OUTPUT_NOTICE_TEXT}`,
+          tag: "drb-attn:on",
+        });
+      } catch {
+        p = "unsupported";
+      }
+    }
     setPerm(p);
     if (p === "granted") onChange({ ...prefs, notify: true });
   };
@@ -215,7 +229,7 @@ export function AttentionControls({ prefs, onChange, armed }: Props) {
             <span>
               <span className="text-ink font-medium">Browser notifications while this tab is hidden</span>
               {perm === "denied" && <span className="block text-ink-muted">Blocked in this browser&apos;s site settings — allow notifications there first.</span>}
-              {perm === "unsupported" && <span className="block text-ink-muted">This browser doesn&apos;t support page notifications.</span>}
+              {perm === "unsupported" && <span className="block text-ink-muted">This browser doesn&apos;t show notifications from a web page (mobile browsers often only allow them from installed apps).</span>}
             </span>
           </label>
           <div>