dsh-web-fetch-proxy: WebFetchProvider with Outbound Proxy

DeepSeek Harness (DSH)'s `ctx.web` performs a default check that the IP is public, causing web fetching to fail in TUN or fake-IP mode. dsh-web-fetch-proxy is a pure registry extension that uses the Cordis Patch mechanism to take over the `web` seam and forwards requests through a user-configured HTTP(S) proxy, thereby bypassing local DNS validation. This plugin requires DSH version 0.1.2-alpha.3 or 0.1.5-rc.1. After installation, configure `proxyUrl` in the profile and point `fetchProvider` to the plugin ID. Because the plugin does not perform local DNS validation, the proxy is the trust boundary; configuration changes