Coalesce fleet refreshes and suppress unchanged sweep events

src/lib/ui/stores/fleet.ts

@@ -124,12 +124,37 @@ export function startFleetMonitor(): () => void {
     if (!browser || stop) return () => {};
     const stopPolling = pollVisible(() => refreshFleet(), 60_000, !get(fleet).receivedAt || Date.now() - get(fleet).receivedAt > 30_000);
     let refreshTimer: ReturnType<typeof setTimeout> | undefined;
+    let stopped = false;
+    let pending = false;
+    let refreshing = false;
+    let lastEventRefresh = -Infinity;
+    const schedule = () => {
+        if (stopped || refreshing || refreshTimer !== undefined || !pending || document.visibilityState === 'hidden') return;
+        refreshTimer = setTimeout(async () => {
+            refreshTimer = undefined;
+            refreshing = true;
+            try {
+                // Wait for any manual/poll refresh, then fetch evidence newer than
+                // the event. Do not use refreshFleet(true)'s immediate follow-up.
+                if (inFlight) await inFlight;
+                if (stopped || document.visibilityState === 'hidden') return;
+                pending = false;
+                lastEventRefresh = Date.now();
+                await refreshFleet();
+            } finally {
+                refreshing = false;
+                schedule();
+            }
+        }, Math.max(250, lastEventRefresh + 2000 - Date.now()));
+    };
     const changed = () => {
-        if (refreshTimer || document.visibilityState === 'hidden') return;
-        refreshTimer = setTimeout(() => { refreshTimer = undefined; void refreshFleet(true); }, 250);
+        if (document.visibilityState === 'hidden') return;
+        pending = true;
+        schedule();
     };
     window.addEventListener('ec:fleet-changed', changed);
     stop = () => {
+        stopped = true;
         stopPolling(); clearTimeout(refreshTimer); window.removeEventListener('ec:fleet-changed', changed); stop = null;
     };
     return stop;