dsh-plugin-collapsible-steps: Collapsing Consecutive Steps to Improve Readability

`dsh-plugin-collapsible-steps` is a DeepSeek Harness (DSH) web plugin designed to reduce interface visual noise by collapsing consecutive debug step cards. It automatically merges consecutive steps such as tool-call and workflow-run into `+ N steps` entries, with centralized collapse/expand control in the conversation header. Users can enable collapsed-by-default in settings. The plugin implements its functionality by annotating the DOM, relies on the base conversation UI, and remains compatible with existing cards, making it suitable for developers who need to keep the interface clean when handling large amounts of debug information.