dsh-diff-approval: Review pending file changes in DeepSeek Harness

dsh-diff-approval is a DeepSeek Harness (DSH) plugin designed to unify the review of file changes generated by agents via edit, write, and str_replace_editor. The plugin automatically records successful modifications, generates a pending list in the sidebar, and provides a comprehensive file diff view featuring syntax highlighting, line search, and virtualized lines. Its core functionality includes multi-level control options: users can perform Keep or Revert operations on individual code blocks, drag-selected line ranges, entire files, or all changes. Additionally, the plugin supports Ctrl+Z/Ctrl+Y for undo and redo, keyboard shortcuts for quickly switching files, copying line references to the composer, and an optional side-by-side comparison view.