dsh-chat-widener: Widen the DeepSeek Harness Web UI Chat Area

`dsh-chat-widener` is a lightweight plugin maintained by garrisonz that injects pure CSS to override the default column width in the DeepSeek Harness (DSH) Web UI, resolving cramped layout issues with long text, tables, and code blocks. By default, it sets the width to 1200px and supports customization through a configuration file (range: 748–2400px). It does not rely on host logic and remains effective after upgrades. Users can install it via the command line and adjust parameters in the configuration file, achieving a wider conversation display area without modifying source code.