dsh-plugin-doctor: Do a health check before installing the DSH plugin

dsh-plugin-doctor is an open-source DSH plugin health check tool maintained by lin-cheng-lab (MIT license), designed to address installation risks caused by release candidate (rc) version mismatches within the DSH plugin ecosystem. It registers as a DSH tool, enabling a quick health check with a single command before plugin installation, without requiring additional scripts or permissions. The health check comprises five checks: local environment version baseline, repository accessibility, bundle declaration, peer dependency compatibility with local versions (the core check, correctly handling prerelease rules), and whether build artifacts are committed. The results are categorized into three levels—ok, warn, and danger—and include a structured JSON report along with handling suggestions. Installation is supported via GitHub (not yet released) or local source code, with profi needing to be restarted after installation.