feat(tui): add rate-limit reset redemption to /usage

[jayp-oai]

Why

Codex users can earn personal rate-limit reset credits, but the CLI does not currently provide a way to view or redeem them. The /usage command restored in #27925 is intended to be the entry point for usage-related actions, so reset redemption belongs there rather than in a separate dashed slash command.

Depends on #28143 for the app-server and backend-client reset-credit APIs.

What changed

• Turn bare /usage into a menu with entries for token activity and earned rate-limit resets while preserving /usage daily, /usage weekly, and /usage cumulative.
• Add loading, empty, confirmation, success, retry, and error states with stable redemption request IDs for idempotent retries.
• Show an availability hint only for backend-classified rate-limit errors with credits available.
• Hide the reset entry for workspace accounts.

Validation

• just test -p codex-tui chatwidget::tests::usage - 14 passed.
• Focused idempotency retry test - passed cleanly on rerun.
• just fix -p codex-tui - passed.
• cargo insta pending-snapshots from codex-rs/tui - no pending snapshots.

Examples

[chatgpt-codex-connector]

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