dsh-custom-context-injector: DeepSeek Harness Custom Context Injection Plugin

The `dsh-custom-context-injector` plugin is maintained by LiKanGame and is designed to provide visualized fixed context injection for DeepSeek Harness. It uses a switch and a text box on the settings page to automatically add user-entered text to the model's `systemPrompt`, with persistent storage across sessions. The plugin depends on the DSH dynamic runtime and is integrated by cloning the source code and running `host.js` and `client.js`. It addresses the need for uniformly managing role settings or development guidelines, and includes features such as in-memory caching, disk persistence, and fallback handling.