dsh-env-inspector: Environment Self-Check and Port Management

`dsh-env-inspector` is an environment self-inspection plugin for DeepSeek Harness, providing a visual dashboard to manage system status. Core features include: real-time port detection and safe release (with a core port protection mechanism), displaying system and CLI toolchain status, globally detecting large-model API keys, listing plugin versions, and distinguishing between LAN and public IP addresses. The plugin has zero runtime dependencies, performs local self-inspection without internet access, and strictly protects privacy while preventing plaintext API key leakage.