fix(tui/limits): refresh expired reset windows over HTTP

[cbusillo]

Summary

• Force the rate-limit refresh worker onto HTTP Responses transport so it can observe fresh x-codex-* rate-limit headers, including when the provider is configured for responses_websocket.
• Refresh expired hourly/weekly reset windows immediately, while avoiding repeated refresh loops after a successful post-reset fetch.
• Add focused regression coverage for expired reset windows and refresh transport selection.

Validation

• Manual /limits smoke test with PATH-installed release binary: looks good.
• cargo test -p code-tui rate_limit_refresh --features test-helpers
• cargo test -p code-tui limits_refreshes_when_reset_time_has_passed --features test-helpers
• ./build-fast.sh
• ./pre-release.sh passed: 1663 passed, 4 skipped, 1 leaky
• just local-code-rebuild, then installed clean overlay release binary to PATH target and verified matching SHA256.

Release Notes

Fixes stale /limits reset timing by making the background refresh use HTTP response headers reliably.