A status line + hooks combo that shows how long since your last API call, so you know when your prompt cache has expired (5-minute TTL). Works per-workspace so multiple sessions don't interfere.
Colors:
- Green: cache warm (< 3 min)
- Yellow: getting stale (3-4 min)
- Red: about to expire (4-5 min)
- Red + "expired": cache is gone, consider starting fresh
