dsh-computer-use: Vision, Accessibility, and Interaction Tools for DeepSeek Harness

The DeepSeek Harness (DSH) plugin `dsh-computer-use` provides models with a complete computer operation toolkit, including 18 `computer_*` tools. It supports accessibility observation, visual recognition, and native input operations on Windows (UIA/MSAA/Narrator), macOS, and Linux. It also offers background capture, multi-monitor support, and an independent accessibility loop. After installation, models can operate desktop applications through accessibility interfaces or the visual pathway, even without native image capabilities. Windows native capabilities are currently the primary focus of validation, while contract tests for macOS and Linux have also been completed.