dsh-lab-check: Health Check Metrics

`dsh-lab-check` is a pure Node.js health metrics tool maintained by uckkk, featuring local health self-checks with no network dependency. As a plugin for DeepSeek Harness (DSH), it avoids network latency by using local calculations. The plugin is MIT-licensed, requires specific dependencies to run, and is suitable for lightweight use cases that need health metrics quickly on the local system.