dsh-openspec: OpenSpec Workflow Skills and Command Alias Plugin

The `dsh-openspec` plugin is designed to address the integration of DeepSeek Harness (DSH) with the OpenSpec workflow. It registers OpenSpec’s 12 core skills as `openspec-*` specification skills and provides `/opsx-*` command aliases, supporting invocation by the model and users. The plugin depends on Cordis, is easy to install, manages state through a standard skills registry, and requires no additional runtime configuration.