UX: @ in skill argument syntax conflicts with @ mention autocomplete

Summary

When a skill's argument syntax includes @ as a prefix (e.g. the skill prompts the user to type /skillname @something), typing @ in the input box triggers Claude Code's built-in mention/file autocomplete dropdown. The auto-suggestion that appears then replaces the intended argument text when dismissed or selected, making the skill difficult to invoke as designed.

Steps to Reproduce

1. Have a skill whose usage includes @ as part of the expected argument
2. Type the skill invocation including @ followed by the argument
3. Observe that the @ triggers the autocomplete dropdown

Expected Behavior

Either:

• The @ autocomplete should not trigger inside skill argument position (after a skill name has been recognized), or
• Skill authors should have a way to declare their argument syntax so that @ is treated as a literal character

Actual Behavior

The autocomplete dropdown intercepts the @ keystroke and its suggestion replaces the intended argument.

Impact

Skills that use @ as a meaningful argument prefix are effectively broken from a UX perspective, requiring workarounds like alternative syntax.