Unclear how to add more skills to a project after initialization

Steps to reproduce:

1. Create a Flutter app
2. Run `npx skills add flutter/skills` and select 1 skill to add for the project
3. Decide later you want another skill
4. Run `npx skills add flutter/skills` and select another skill to add to the project

At this point I had `.agent/skills` and `.agents/skills` - `.agent` only had 1 skill, `.agents` had 2.

Note: This was in Antigravity.