dsh-netdoctor: DeepSeek Harness Network Diagnostics Toolkit

`dsh-netdoctor` is a zero-dependency network diagnostics toolkit for DeepSeek Harness, offering agents secure, read-only probes. It provides seven capabilities: DNS queries, ICMP Ping, TCP port probing, TLS certificate analysis, route tracing, public IP lookup, and WHOIS queries. The plugin mitigates injection risks through parameter pinning, input validation, and hard timeouts, and supports optional geolocation so agents can safely and independently diagnose network connectivity and certificate status.