dsh-proxy-gate: Add a switch for DSH outbound traffic per session

DSH's outbound network defaults to direct connection. Temporarily switching to a proxy typically requires modifying the system proxy or the `.env` file and restarting the process; the former affects other programs on the same machine. dsh-proxy-gate is a networking plugin maintained by elliotsu1107 that enables one-click switching of the DSH process's outbound proxy via the `/proxy` command in the plugin settings or a session. When enabled, it replaces the undici global dispatcher with one pointing to the specified proxy, affecting model APIs, `web_search`, `web_fetch`, MCP, plugin downloads, and bash subprocesses; when disabled, it restores the network policy from startup, with loopback addresses always remaining directly connected. This article provides the README installation commands, interface, and usage for six `/proxy` commands, four volatile configuration fields and their defaults, and explains address validation rules, subprocess proxy variable inheritance, and the handling of unreachable proxies. The plugin runs with DSH process privileges; users should review the source code and license before installation.