DSH Plugin: dsh-reset-handoff (Host Reset Handoff Protocol)

The DeepSeek Harness (DSH) plugin `dsh-reset-handoff` resolves the deadlock issue of DSH restarting itself through a “handoff” mechanism. It enables an external operations agent to take over the restart process, exchanging requests and results via a versioned JSON protocol to ensure the process is safe, observable, and recoverable. The plugin supports pre-check snapshots, health checks, and graceful degradation, managing the workflow through the `reset_handoff` and `reset_status` tools, with a reference executor provided by a pure Python script.