Lets a plugin.json declare an `external` target->source map instead of
carrying local content, so the generator emits that Claude Code
marketplace source (e.g. a GitHub repo) verbatim rather than a local
dist path. Adds caveman and ponytail as external entries, installed
straight from their upstream repos with nothing vendored or copied.
Claude Code-only for now — agy has no equivalent external-source
mechanism, and both plugins' hooks/MCP assume Claude Code's runtime.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014YVWWAnvR5TDQzmfY3RXG9
