fix: pr-bug-scan validated finding from #8690

[buf0-bot]

Automated fix-PR from pr-bug-scan for parent #8690.

Fixer status: FIXED_WITH_CODE_PROOF
Summary: In index.tsx wireUp, stop tearing down the notification subscription on non-'connected' states so its stream survives reconnect and reconnectReadyCount can exceed 1, firing fetchMissed.
Blocked proof link: mobile/app/index.tsx:534-536 wireUp's else branch no longer calls unsubNotif()/removeStreamListener; the notifications.subscribe stream now persists across the setState('reconnecting') at rpc-client.ts:732, so replay re-emits 'ready' on the same subscription and reconnectReadyCount reaches 2, satisfying the >1 gate at mobile-notifications.ts:354.
Typecheck: skipped

Proof (from validator)

• C2 — proof_type: code_analysis
  • trigger: Phone backgrounds/sleeps, its WebSocket is reaped, then it foregrounds and the RPC client reconnects — the ordinary background→reconnect cycle on the home screen.
  • observable: notifications.getMissedSince is never called on reconnect; notifications dispatched while the phone's socket was reaped are never fetched or shown. The catch-up feature ([Feature]: Real push notifications for mobile — events are lost while the app is backgrounded/disconnected #8129) is dead code in production.
  • path:
    • mobile/app/index.tsx:514 subscribeToDesktopNotifications is called inside wireUp only when state === 'connected'; this is the only production caller (grep-confirmed).
    • mobile/app/index.tsx:534-536 wireUp's else branch runs on ANY non-'connected' state and calls unsubNotif() (the subscription's returned cleanup), setting unsubNotif=null.
    • mobile/src/transport/rpc-client.ts:1187 that cleanup ends in removeStreamListener(id), deleting the notifications.subscribe stream so the reconnect replay loop cannot re-emit 'ready' on it.
    • mobile/src/transport/rpc-client.ts:732 (and :768) every socket close calls setState('reconnecting') before any reconnect, guaranteeing wireUp's teardown fires first — no reconnect keeps state 'connected'.
    • mobile/app/index.tsx:511-514 on the subsequent 'connected' transition wireUp constructs a brand-new subscription.
    • mobile/src/notifications/mobile-notifications.ts:335 the new subscription initializes reconnectReadyCount = 0, so its first (reconnect) 'ready' at :344 only reaches count 1.

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Generated by pr-bug-scan (proof-machine architecture). Human approval required before merge.