docs(agents): update skill install example to include universal flag and clarify usage

dot_agents/skills/find-skills/SKILL.md

@@ -98,10 +98,10 @@ Learn more: https://skills.sh/vercel-labs/agent-skills/react-best-practices
 If the user wants to proceed, you can install the skill for them:
 
 ```bash
-npx skills add <owner/repo@skill> -g -y
+npx skills add <owner/repo@skill> -g -y -a universal claude-code
 ```
 
-The `-g` flag installs globally (user-level) and `-y` skips confirmation prompts.
+The `-g` flag installs globally (user-level), `-y` skips confirmation prompts, and `-a universal claude-code` installs to `~/.agents/skills` with a symlink in `~/.claude/skills`. Always pass `-a`: without it, skills CLI 1.7.0 adds project-only PromptScript to global installs and reports `PromptScript does not support global skill installation`.
 
 ## Common Skill Categories