dsh-update-radar: Check installed link: plugins for upstream updates

dsh-update-radar is an MIT-licensed tool adhering to the "everything is a plugin" philosophy of DeepSeek Harness, maintained by Equinox7379. This plugin is used for read-only checks to determine whether multiple `link:` local plugin directories in the configuration are behind the upstream version. Its core mechanism involves reading dependency paths from the profile, executing `git rev-parse` and `git ls-remote` commands on directories containing `.git`, and comparing local and remote HEAD hashes. The tool provides a parameterless `update_radar` interface, generating a JSON report containing `checked`, `behind` (indicating a version behind), and `upToDate` (indicating the latest status). The process is complete.