dsh-m: DeepSeek Harness Plugin Marketplace

dsh-m is the unified plugin management tool for DeepSeek Harness (DSH), designed to address the challenges of fragmented plugin sources and inconsistent management entry points. It integrates the sidebar panel, Agent tools, and the command line (`dshm` CLI) to provide a unified search, installation, upgrade, and uninstallation experience. The tool supports dual-source search (community catalog and curated selections), uses npm package version locking and GitHub commit SHA verification for security, and allows custom sources via HTTPS, local paths, and other options. After installation, users can operate through the `dshm` command line or the plugin interface. Note that the community catalog is not security-reviewed, uninstallation does not automatically remove data, and the Desktop host must be restarted manually.