dsh-persona: Adding a Collaborative Style Layer to DeepSeek Harness

`dsh-persona` is a dual-end plugin for DeepSeek Harness, designed to add a configurable layer of collaborative style to model outputs. It appends system prompts to requests to optimize communication tone and progress reporting, without changing DSH's core logic or security policies. Users can select built-in styles such as “Friendly Collaboration” or “Pragmatic and Direct” in the web interface, or customize them using “Shared Prompt Blocks.” Once installed and enabled, the plugin takes effect at runtime, helping developers standardize the collaborative behavior of models.