Feature request: Pin/favorite skills in slash command menu

Problem

Power users with 15+ skills installed have no way to surface their most-used skills at the top of the / slash command menu. All skills appear in a flat list, making it slow to find frequently-used ones — especially for visual users who don't always remember exact skill names.

Suggested solution

Allow users to pin or favorite skills so they appear first in the / menu. Two possible implementations:

1. Frontmatter field — add pinned: true in SKILL.md frontmatter
2. Settings-based — a favoriteSkills list in settings.json

Current workaround

Prefixing skill names with _ (e.g. _full-report, _recherche) — underscore sorts before letters in ASCII, so /_ filters to just the favorites. Works but is a hack that changes the invocation command.

Context

Use case: algorithmic trading workflow with 15+ custom skills (research, backtest reports, code review, investigation, shipping, etc.). A handful are used in 80%+ of sessions.

No existing issue found for this feature.