dsh-prompt-persona: Editing DSH System Prompt on Settings Page

@xilin3/dsh-prompt-persona is a DSH client plugin maintained by Xilin3, taking over the editing and persistence of deployment:persona on the web settings page. It supports three injection modes: replace, append, and off, along with real-time preview of the complete system prompt, optimistic concurrency saving based on revision, and template variables such as {{model}}, {{cwd}}, and {{provider}}. After installation, simply restart the DSH web to adjust the agent's role settings directly on the settings page, without modifying the Harness itself or manually writing a cordis.patch.yml file.