dsh-diff-view: A Universal Diff Viewer Plugin for DeepSeek Harness

`dsh-diff-view` is a lightweight client plugin for DeepSeek Harness (DSH) that provides plugin developers with a general-purpose text diff viewing capability, eliminating the need to hand-write Diff algorithms. It operates through service injection. Its core features include line-level comparison based on the LCS algorithm, word highlighting, Split/Unified view switching, and syntax highlighting consistent with the native Review. The plugin supports rendering full file diff components and provides a low-level engine for retrieving diff chunks and line alignment data. Developers can reuse its styling and rendering logic by simply installing and injecting the service.