Install Structured Difference Comparison for DeepSeek Harness with dsh-tool-diff

`dsh-tool-diff` is a DeepSeek Harness tool plugin maintained by `omdsh-dev`, which registers a diff tool to perform structured comparison on text, JSON, CSV and Markdown and output unified diff. It features zero dependencies, pure functions and read-only, and patches are only verified in memory. This article verifies the installation commands, five actions, input and output budgets, and the installation notes for web/headless environments according to the community directory page and GitHub README.