dsh-subagent: DeepSeek Harness Subagent Configuration Plugin

`dsh-subagent` is a community plugin for DeepSeek Harness that aims to address the challenges of cumbersome manual configuration and difficult reuse by converting named configurations into tools. It supports managing configurations through the Web UI and allows the Root Agent to delegate specific tasks via tool calls (e.g., `subagent_<name>`). The plugin’s core features include context modes (spawn/fork), routing policy selection, inference configuration adjustment, and hot updates. During installation, a Profile with the Web runtime loaded must be specified, making it suitable for developers who need to reuse multi-model combinations and inference strategies.