Use dsh-git-identity to fix DeepSeek Harness's git commits to the environment's own identity

`dsh-git-identity` is a DeepSeek Harness development and runtime plugin maintained by LoserFox. At load time, it parses the author identity from plugin configuration, gh CLI, startup environment variables, and `git config --global`, writes them into `GIT_AUTHOR_*` / `GIT_COMMITTER_*` to override subsequent Git configurations, and can idempotently write back to the global identity. The directory installation command is `dsh plugin add github:LoserFox/dsh-git-identity`. The community repository is not an official store, so you need to check the source code before installation; no license has been declared for the repository yet.