aitmpl, at https://www.aitmpl.com/marketplace.json. Each entry points at the author’s repository, pinned to the commit that was reviewed and scanned.
claude plugin marketplace add and claude plugin install champion-kit@aitmpl), so the files land in ~/.claude/plugins/cache/aitmpl/ and you manage the plugin with /plugin like any other. If claude is not on your PATH, the CLI writes the same two settings keys (the marketplace and the enabled plugin) instead, and Claude Code offers to install the plugin the next time it starts in that folder.