Feat(statusline): show rate-limit reset countdown

Summary

Add a live reset countdown to the status line’s rate-limit entries, for example:

weekly 98% left · reset 3d:5h:21m

Implementation

The feature is implemented and pushed in the fork branch:

• Fork: kotov228/codex
• Branch: agent/status-line-reset-countdown
• Commit: 2cfb8f011f

It updates both five-hour-limit and weekly-limit, refreshes once per minute, and keeps terminal-title output consistent.

Validation

• just test -p codex-tui — 3082 passed, 4 skipped
• cargo fmt --check
• git diff --check

The automated pull-request creation endpoint currently returns a permissions error, but the branch is ready for review.