[BUG] Delivered mobile push notifications are never revoked once the session has moved on (re: #76900)

Summary

Push notifications delivered to the iOS Claude app are never withdrawn. When a session pushes "Claude has a question" and the question is then answered on another device — or the session simply moves past that point — the notification stays in the iOS notification center indefinitely and has to be swiped away by hand.

This is a re-file of #76900, which had a confirmed repro and carried bug / has repro / platform:ios, but was closed not planned by the stale bot on 2026-09-03 with no human response. The bot's closing message invites a new issue if the problem is still relevant. It is: I hit it daily on 2.1.231.

Steps to reproduce

1. Run one or more sessions with mobile push enabled (inputNeededNotifEnabled: true, agentPushNotifEnabled: true).
2. Let a session reach a point where it needs input. A push arrives on the iPhone.
3. Answer it on the desktop — the session continues and no longer needs anything.
4. Look at the phone's lock screen.

Expected

The notification is withdrawn on the other devices once the session no longer needs input, the way multi-device messaging apps revoke a notification after it is acted on elsewhere. APNs supports both mechanisms: apns-collapse-id to coalesce per session, and a Notification Service Extension to remove already-delivered notifications.

Actual

Every notification ever pushed is still on the lock screen. Tapping one opens a session that is long past that question. Running several sessions a day, the lock screen becomes a wall of questions that were all resolved hours ago — and because none of them are actionable, the ones that are stop being noticed. That is the real cost: the notification channel loses its signal.

Two consequences worth separating:

• No revocation — an answered question's notification is never removed.
• No coalescing — a single session that asks several times leaves one notification per question, rather than one live notification per session.

Environment

• Claude Code 2.1.231
• macOS 26.6.2 (25G83), arm64
• iOS Claude app, current App Store build
• ~/.claude/settings.json: inputNeededNotifEnabled: true, agentPushNotifEnabled: true

Note

Distinct from the "push not delivered" reports (#60208, #50949, #30592) — delivery works fine here; revocation is what is missing.

Minor, and a change since #76900 was filed: neither inputNeededNotifEnabled nor agentPushNotifEnabled appears in the settings reference at https://code.claude.com/docs/en/settings.md any more. #76900 noted only the first as undocumented; both are now absent, while both still have an effect.