Keep focused agent timelines live and catch up instantly (#2196)

* fix(app): keep focused agent timelines live

Window focus was conflated with app visibility, so switching OS windows could remove the selected timeline subscription. Separate those signals, grace every visibility-driven removal, and cover retained history until authoritative catch-up completes.

* fix(app): keep timeline catch-up failures non-blocking

* fix(app): surface timeline catch-up failures

* fix(app): preserve file preview refocus

* fix(app): preserve optimistic catch-up flow

packages/app/src/hooks/use-app-visible.ts

@@ -1,19 +1,24 @@
 import { useSyncExternalStore } from "react";
 import { AppState } from "react-native";
-import { getIsAppActivelyVisible } from "@/utils/app-visibility";
+import { getIsAppActivelyVisible, getIsAppVisible } from "@/utils/app-visibility";
 import { isWeb } from "@/constants/platform";
 
-let current = getIsAppActivelyVisible();
-const listeners = new Set<() => void>();
+let visible = getIsAppVisible();
+let activelyVisible = getIsAppActivelyVisible();
+const visibilityListeners = new Set<() => void>();
+const activeVisibilityListeners = new Set<() => void>();
 
 function notify(): void {
-  const next = getIsAppActivelyVisible();
-  if (next === current) {
-    return;
+  const nextVisible = getIsAppVisible();
+  if (nextVisible !== visible) {
+    visible = nextVisible;
+    for (const listener of visibilityListeners) listener();
   }
-  current = next;
-  for (const listener of listeners) {
-    listener();
+
+  const nextActivelyVisible = getIsAppActivelyVisible();
+  if (nextActivelyVisible !== activelyVisible) {
+    activelyVisible = nextActivelyVisible;
+    for (const listener of activeVisibilityListeners) listener();
   }
 }
 
@@ -29,15 +34,32 @@ if (isWeb && typeof document !== "undefined") {
   window.addEventListener("blur", notify);
 }
 
-function subscribe(listener: () => void): () => void {
-  listeners.add(listener);
-  return () => listeners.delete(listener);
+function subscribeToVisibility(listener: () => void): () => void {
+  visibilityListeners.add(listener);
+  return () => visibilityListeners.delete(listener);
 }
 
-function getSnapshot(): boolean {
-  return current;
+function subscribeToActiveVisibility(listener: () => void): () => void {
+  activeVisibilityListeners.add(listener);
+  return () => activeVisibilityListeners.delete(listener);
+}
+
+function getVisibilitySnapshot(): boolean {
+  return visible;
+}
+
+function getActiveVisibilitySnapshot(): boolean {
+  return activelyVisible;
 }
 
 export function useAppVisible(): boolean {
-  return useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+  return useSyncExternalStore(subscribeToVisibility, getVisibilitySnapshot, getVisibilitySnapshot);
+}
+
+export function useAppActivelyVisible(): boolean {
+  return useSyncExternalStore(
+    subscribeToActiveVisibility,
+    getActiveVisibilitySnapshot,
+    getActiveVisibilitySnapshot,
+  );
 }