Automatically apply banked resets before they expire

What variant of Codex are you using?

Codex in the unified ChatGPT app on macOS

What feature would you like to see?

Problem

Banked usage resets can expire unused if a user saves one for later, forgets the expiry, is away, or is not shown the exact expiration time.

There is little reason to discard an unused reset when it could still provide value.

Proposed behavior

By default, Codex should:

1. Keep the reset available for manual use until shortly before expiry.
2. Apply it automatically if it remains unused.
3. Process redemption server-side, even when the app is closed.
4. Show the exact expiry time and notify the user when automatic redemption occurs.
5. Allow this behaviour to be disabled in settings.

The reset should be applied at the latest safe moment and should not reduce or overwrite a more valuable existing allowance.

Additional information

This would complement #32218, which proposes redeeming a queued reset when a usage limit is reached:

manual use → queued use at limit → automatic use before expiry

Related issues: #32218, #28805, and #32540.