Add Xquik social automation skill and repair the registry index

[kriptoburak]

Summary

• add xquik-social-automation for public X search, analytics, monitoring, webhooks, and approval-gated publishing
• document current OAuth 2.1 setup for https://xquik.com/mcp
• document REST API-key usage through the x-api-key header
• include Xquik's independence and trademark notice

Independent repository fix

registry.json says it indexes every item, but current upstream listed only multi-brain while 5 top-level skill manifests exist. This repair adds all 5 existing manifest-backed skills, normalizes their identity fields to their manifests, sets generated_at, and includes Xquik as the sixth entry.

The branch was rebuilt from current upstream. It preserves all skills published after the original PR and removes the old branch's accidental 83-file deletion diff.

Validation

• parsed registry.json and every top-level manifest.json
• verified 6 unique registry slugs and exact registry-path coverage
• verified registry kind, slug, name, author, and version against each manifest
• verified the Xquik sha256 matches SKILL.md
• verified the live Xquik MCP manifest reports version 2.5.4, Streamable HTTP, and OAuth 2.1
• verified the live OpenAPI security scheme uses x-api-key
• git diff --check