[Feature Request] Add per-skill granular control for plugin management

Question

**Request Description**
Currently, plugins are all-or-nothing - you can only disable an entire plugin, not specific skills within it.

I'd like to be able to disable individual skills from a plugin while keeping others active. For example, keep a plugin's core features but hide skills I don't use from cluttering suggestions.

Possible approaches:
  - A /plugin disable-skill plugin-name:skill-name command
  - A config option in settings.json to exclude specific skills
  - Per-skill toggle in