dsh-project-mcp: Configuring MCP Servers for Project-Level Sessions

The DSH plugin `dsh-project-mcp` introduces a project-level MCP server configuration scope, allowing developers to isolate MCP services for specific projects (such as Rider and Playwright) in a local `mcp.json` to avoid interference from global configuration. It supports lazy loading, variable substitution, idle release, and error tolerance mechanisms. Installation requires packaging with `pnpm pack` and adding the package to the GUI. Configuration follows a global-first precedence principle, and sensitive files such as `.env` should be handled carefully to ensure version-control security.