Remove starter boilerplate from plugin repo

[n2parko]

Summary

• replace the copied starter marketplace entries with the real root firetiger plugin manifest and marketplace registration
• remove leftover starter plugin files and template docs that were accidentally checked in
• keep the README hero image while updating the docs and validator to match the actual single-plugin repo layout

Test plan

• Run node scripts/validate-template.mjs
• Run git diff --check
• Verify rendered README on GitHub

Made with Cursor

[achille-roussel]

Magic 🙏