dsh-htb-skills: Hack The Box Skills Library Plugin

The HTB Skill Library plugin for DeepSeek Harness (DSH) is designed to address fragmented skill management by encapsulating the HTB skill library. It provides 114 skill cards spanning multiple domains, uses versioned management and a hierarchical structure (T1/T2/T3), and supports hot reloading and HTB API integration. Users must have DeepSeek Harness 0.1.0-rc.x and Node.js 22.19.0+ installed. After installing the plugin, standalone skills with the same names will be shadowed; it is recommended to back up and migrate them. Additionally, this is a community project in developer preview, so potential breaking changes should be considered when upgrading.