Unclear how to add more skills to a project after initialization

[elliette]

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.