Plugin skills not visible in initial `/` slash command list

Plugin-provided skills (e.g., /claude-mem:do, /repomix-commands:pack-local) don't appear when typing / and scrolling the initial autocomplete dropdown. They only start appearing after typing additional characters that match the skill name.

Expected: Plugin skills should be discoverable in the initial / list — either inline or in a separate "Plugins" section.

Current behavior: Only built-in commands and locally-defined skills appear in the initial dropdown. Users must already know the plugin skill name prefix to find them.

Steps to reproduce:

1. Install any plugin that provides skills (e.g., claude-mem, repomix-commands)
2. In a conversation, type / and scroll the autocomplete list
3. Plugin skills are not listed
4. Type /claude-m or /repo — plugin skills now appear

Environment: Claude Code CLI (macOS)