Add origin field to all skill files to track their source repository.
This enables users to identify where distributed skills originated from.
Fixesaffaan-m/everything-claude-code#246
New skill: /security-scan wraps ecc-agentshield to audit .claude/ configs
for vulnerabilities, misconfigs, and injection risks.
Covers: CLAUDE.md secrets, settings.json permissions, MCP server risks,
hook injection, agent tool restrictions. Produces A-F security grade.
Also adds AgentShield section to Ecosystem Tools in README with
links to GitHub repo and npm package.