Distribution: publish MCP server to PyPI (uvx), add Claude Code plugin manifest, list on Cursor marketplace and MCP registries #41

Why it matters

Right now the only way to get the MCP server is to clone the repo and pip install inside it, and the project is not discoverable where Unity developers look for AI tooling. CLAUDE.md claims Claude Code support, but there is no Claude Code plugin manifest. Distribution is the main growth lever for a 4-star project.

Proposal

1. PyPI package for the MCP server (unity-developer-tools-mcp), runnable with uvx unity-developer-tools-mcp or pipx. Data files packaged as package data (also fixes the CWD bug). Publish from release.yml with trusted publishing.
2. Claude Code plugin: add .claude-plugin/plugin.json and .mcp.json so the same skills and MCP server install via /plugin; document it in README.
3. Cursor marketplace submission (roadmap M4), with screenshots and a short demo.
4. MCP registries: list on the official MCP registry and common directories (Smithery, mcp.so, Glama), and in awesome-cursor / awesome-mcp-servers / awesome-unity lists.
5. One-click install link / deeplink for Cursor MCP config in README.

Done when

A user can install the server with one command, install the plugin from Cursor or Claude Code without cloning, and the project appears in at least two MCP directories.