izwarm195/dsh-net-tools: Connect DSH to local HTTP proxy

dsh-net-tools is an MIT-licensed plugin designed specifically for DSH agents, aiming to address the issue where agents inside a sandbox must access external networks via a local HTTP proxy. The plugin provides two core tools, `net_fetch` and `net_proxy_status`: the former fetches HTTP(S) content via a manual CONNECT tunnel, supports automatic redirection, and includes built-in security checks such as protocol restrictions, a 30-second timeout, a 1 MiB response size limit, and default rejection of private network addresses; the latter detects the actual proxy configuration and reachability used by the DSH process by checking environment variables and Windows system proxy settings in sequence. Users only need to install and restart DSH, provided Node.js 20 or higher is installed, to utilize these tools in the Agent.