Add agentskill-learn skill

Author: romainsimon

skills/agentskill-learn/SKILL.md

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+---
+name: agentskill-learn
+description: "Discover, install, and manage AI agent skills from agentskill.sh marketplace. Search 44,000+ community skills by keyword, install mid-session with security scanning, and rate skills after use. Use when asked to find skills, extend capabilities, or learn new tools."
+---
+
+# AgentSkill Learn — Community Skills Marketplace
+
+This skill connects GitHub Copilot to [agentskill.sh](https://agentskill.sh), a community marketplace for AI agent skills. Search, install, and manage skills with built-in security scanning.
+
+## Installation
+
+This is a pointer to the canonical skill. Install the full version:
+
+```bash
+gh copilot skill install https://github.com/agentskill-sh/learn
+```
+
+## What It Does
+
+- **Search**: Find skills by keyword from the agentskill.sh catalog (44,000+ skills indexed)
+- **Install**: Download skills with security scanning (blocks dangerous patterns)
+- **Rate**: Auto-rate skills after use; user ratings override
+- **Update**: SHA-based version tracking for updates
+- **Multi-platform**: Works with Copilot, Claude Code, Codex, Cursor, Windsurf, Cline
+
+## Quick Commands
+
+| Command | Description |
+|---------|-------------|
+| `/learn <query>` | Search for skills |
+| `/learn @owner/slug` | Install specific skill |
+| `/learn trending` | Show trending skills |
+| `/learn list` | Show installed skills |
+| `/learn update` | Check for updates |
+| `/learn scan <path>` | Security scan a skill |
+
+## Security
+
+**Two-layer security model:**
+
+1. **Registry-side**: All skills pre-scanned at publish time with pattern detection (command injection, data exfiltration, prompt injection, credential harvesting, obfuscation)
+2. **Client-side**: Score displayed before install; skills below 70 blocked, 70-89 require acknowledgment
+
+| Score | Action |
+|-------|--------|
+| 90-100 | SAFE — install proceeds |
+| 70-89 | REVIEW — requires acknowledgment |
+| <70 | BLOCKED — installation refused |
+
+## Links
+
+- **Marketplace**: https://agentskill.sh
+- **Source**: https://github.com/agentskill-sh/learn
+- **Report Issues**: https://github.com/agentskill-sh/learn/issues