dsh-at-skill: Invoking Skills via @name in DeepSeek Harness

dsh-at-skill is a standalone plugin for extending skill invocations without modifying the Harness source code. Users can trigger a skill by typing `@name` in the conversation composer; the system will automatically list suggestions or filter candidates by prefix. The plugin loads and executes the skill before the model step, remaining compatible with existing invocation behavior. To install it, run the designated command and restart `dsh web`. Note that the text-based invocation mechanism may cause confusion among Skills, Subagents, or Plugins with the same name, and the service must be restarted after installation for changes to take effect.