dsh-cordis: Wrapping DeepSeek Harness as a Cordis Plugin

`dsh-cordis` is a package that wraps the DeepSeek Harness (DSH) coding engine as a Cordis plugin, aiming to simplify the integration of DSH capabilities into the Cordis ecosystem. By using compositional mounting and native service providers, it injects DSH capabilities such as agents, sessions, and tools into the host Loader tree, supporting dependency injection rather than direct imports. The plugin has no standalone root, Fiber is owned by the caller, and telemetry is disabled by default, making it suitable for developers who need to reuse DSH capabilities within Cordis plugins.