dsh-guard: A Companion Guard Plugin for DSH Development

`dsh-guard` is a guardian plugin in the DeepSeek Harness ecosystem that ensures plugin stability. It uses automated mechanisms to address runtime uncertainty. Its core capabilities include rolling snapshots (retaining the latest N snapshots and mirroring `last-good`), automatic archiving, automatic rollback on failure, a Web management panel, and a RESTful API. The plugin includes a loop-prevention mechanism, allowing only one automatic rollback per startup. Configuration supports a grace period and custom parameters. Note that it cannot handle startup crashes and is limited to local access.