Feature Request: Show skill usage count and last-used time in /skills

What feature would you like to see?

Problem: I have many skills installed, but it’s hard to tell which ones actually trigger. I don’t know how often a skill is used or when it last ran. This makes it harder to keep my skill list lean and avoid wasting context on rarely used skills.

Proposed solution:
Add usage stats to /skills (and/or codex skills) output:
Usage count
Last used timestamp (relative + ISO)
Track both explicit invocations and auto-triggered uses.
Store stats locally (no server sync), with a way to reset (e.g., --reset-stats) and/or a --json view for scripts.

Why this helps:
Identify rarely used skills to disable/remove.
Reduce context overhead from skills that never trigger.
Make it easier to tune skill descriptions for better triggers.

Additional information

Happy to help validate the UX or contribute a PR if there’s alignment.