dsh-continuum: Persistent State and Checkpoint Engine for DeepSeek Harness

`dsh-continuum` is a production-grade plugin for DeepSeek Harness (DSH), designed to address issues such as state loss, context exhaustion, and process crashes in agent collaboration. It transforms DSH into an engineering environment with persistent memory and fault tolerance. Through event sourcing, optimistic concurrency control, and strict context budget management, the plugin provides core capabilities including data recovery, secure locking, four-eyes verification, and content encapsulation. Developers can use its tools to manage the full project lifecycle and transition from one-off scripts to continuous engineering.