Keep argument-hint visible while typing and add option selection

Current Behavior

When using slash commands with argument-hint in the frontmatter, the hint is displayed nicely when I type /<command_name>. However, once I type the first character after the command name, the suggestions/hints disappear, making it harder to recall the available arguments.

Requested Improvements

1. Keep hints visible while typing

The argument-hint should remain visible (perhaps dimmed) as the user types the command and its arguments, so they can reference the expected format.

2. Selectable options for pre-specified values

When argument-hint contains enumerated options like:

argument-hint: [GROUP="all|foundation|scheduler|observer"]

Claude Code could parse the |-separated values and present them as a selectable dropdown/list, similar to how IDE autocomplete works.

Example

---
description: Audit implementation against specs
argument-hint: [GROUP="all|foundation|scheduler|observer|workers"]
---

When the user types /audit and the cursor is at the GROUP position, show a picker:

• all
• foundation
• scheduler
• observer
• workers

Benefit

This would significantly improve the UX for custom skills with complex arguments, reducing the need to memorize argument formats or check documentation.