[codex] Fix usage-limit reset copy and state

[jayp-oai]

Why

The reset flow introduced in #28154 still describes earned reset credits as "rate-limit resets" and uses generic reset-scope copy. It can also retain a stale available-credit count after redemption or an account change, leaving the reset action enabled after the last credit is used.

This follow-up updates terminology only within that reset feature. Existing rate-limit wording elsewhere in the CLI and TUI is unchanged.

What changed

• Rename reset-specific /usage menu items, startup hints, and reset dialogs to "usage limit reset."
• Describe monthly resets for Free, Go, and accounts that report a monthly usage window; otherwise describe the current 5-hour and weekly limits.
• Recheck a cached zero balance when /usage is reopened, and refresh the balance after redemption so the final reset immediately disables the action.
• Correlate async refresh results before updating snapshots and clear account-derived reset state, warnings, prompts, and status surfaces when the account changes.

Validation

• just test -p codex-tui chatwidget::tests::usage — 29 passed.
• just test -p codex-tui chatwidget::tests::status_command_tests — 7 passed.
• Account-boundary prompt and plan-mode prompt regression tests passed.
• cargo insta pending-snapshots from codex-rs/tui — no pending snapshots.\

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