fix(notifications): never suppress push when clients.matchAll() returns empty

The TTL-gated appIsVisibleFresh fallback was designed to handle the iOS
Safari PWA quirk where clients.matchAll() returns an empty list even
when the app is visually open.  In practice, the TTL window (30 s) meant
any push that arrived within 30 seconds of the app being last visible was
silently dropped — including the common case of backgrounding the app
and immediately receiving a reply.

pagehide + visibilitychange together are now much more reliable at
delivering setAppVisible:false before the SW processes the push.  When
both events DO fail (iOS kills the JS context mid-event), clients.matchAll()
ALSO tends to return the backgrounded client as visibilityState:'hidden',
which is already handled correctly by the first branch.

The clients.length === 0 path is therefore a triple-failure edge case
where we simply cannot determine visibility.  Erring toward showing the
notification (a possible duplicate, handled gracefully by the in-app
banner) is always better than silently dropping it.

Removes appVisibleSetAt, APP_VISIBLE_TTL_MS, and the stale-flag fallback.

Author: Just-Insane

src/sw.ts

@@ -12,13 +12,6 @@ let notificationSoundEnabled = true;
 // The clients.matchAll() visibilityState is unreliable on iOS Safari PWA,
 // so we use this explicit flag as a fallback.
 let appIsVisible = false;
-// Timestamp (Date.now()) of the last time appIsVisible was set to true.
-// Used to expire the flag if the app backgrounded before the SW received the
-// hidden message (e.g. iOS suspended the JS context mid-visibilitychange).
-let appVisibleSetAt = 0;
-// If no visible heartbeat has been received in this window, treat the flag as
-// stale and do not suppress push notifications.
-const APP_VISIBLE_TTL_MS = 30_000;
 let showMessageContent = false;
 let showEncryptedMessageContent = false;
 let clearNotificationsOnRead = false;
@@ -578,7 +571,6 @@ self.addEventListener('message', (event: ExtendableMessageEvent) => {
   if (type === 'setAppVisible') {
     if (typeof (data as { visible?: unknown }).visible === 'boolean') {
       appIsVisible = (data as { visible: boolean }).visible;
-      if (appIsVisible) appVisibleSetAt = Date.now();
     }
   }
   if (type === 'setNotificationSettings') {
@@ -758,21 +750,20 @@ const onPushNotification = async (event: PushEvent) => {
   // If the app is open and visible, skip the OS push notification — the in-app
   // pill notification handles the alert instead.
   //
-  // Two-tier visibility check:
-  // 1. When clients.matchAll() returns ≥1 client, trust its visibilityState
-  //    directly.  iOS can suspend the JS thread before postMessage({ visible:
-  //    false }) is processed, leaving appIsVisible stuck at true.  matchAll()
-  //    still reports the backgrounded client as 'hidden', so it is the
-  //    authoritative signal when available.
-  // 2. When matchAll() returns zero clients (a separate iOS Safari PWA quirk
-  //    where the page is invisible to the SW even while visible), fall back to
-  //    the TTL-gated flag: the flag expires after APP_VISIBLE_TTL_MS so a stale
-  //    true from a quick background doesn't permanently suppress notifications.
-  const appIsVisibleFresh = appIsVisible && Date.now() - appVisibleSetAt < APP_VISIBLE_TTL_MS;
+  // When clients.matchAll() returns ≥1 client, trust its visibilityState
+  // directly.  iOS can suspend the JS thread before postMessage({ visible:
+  // false }) is processed, leaving appIsVisible stuck at true.  matchAll()
+  // still reports the backgrounded client as 'hidden', so it is the
+  // authoritative and most reliable signal.
+  //
+  // When matchAll() returns zero clients (a separate iOS Safari PWA quirk),
+  // visibility is unknowable — do NOT suppress.  Better to show a duplicate
+  // (handled gracefully by the in-app banner) than to silently drop a
+  // notification while the app is backgrounded.
   const hasVisibleClient =
     clients.length > 0
       ? clients.some((client) => client.visibilityState === 'visible')
-      : appIsVisibleFresh;
+      : false;
   console.debug(
     '[SW push] appIsVisible:',
     appIsVisible,