support the skills func based on the claude agent skills

**Is your feature request related to a problem? Please describe.**
> No

**Describe the solution you'd like**
> Skills is the future for the ai coding problem to solve.

**Describe alternatives you've considered**
>

**Additional context**
>

The issue names no files, tests, or entry points. Start by clarifying which Claude agent skills behavior OxyGent should support and where skills are integrated; define the supported behavior and acceptance tests before implementation.

Written by the indexing model from the issue text.