Consider merging Skills and Slash Commands

Skills and Slash Commands seem to function almost identically:

• Both can be invoked by the user with a slash prefix
• Both can be invoked by Claude itself
• Both load instructions into the conversation

The main difference appears to be intent (skills = Claude-invoked primarily, commands = user-invoked primarily), but in practice they work the same way.

Would it simplify things to merge these into a single feature? Perhaps with a flag to control whether it appears in autocomplete or is primarily model-invoked?