dsh-git-seam: Structured Git Tools and Commit Gating for DeepSeek Harness

`dsh-git-seam` is a Git plugin designed for DeepSeek Harness agents to address issues of blind commits and unreliable parsing. It provides six structured tools and a “Diff-Before-Commit” gate mechanism, requiring agents to review changes before committing to keep operations secure and controllable. The plugin supports viewing status, diffs, logs, branches, and commits, but is limited to local operations and does not support destructive history operations, remote pushes, or certain advanced features. It is simple to install and configure, making it suitable for DSH workflows that require strict commit review.