dsh-mac-cua: macOS Computer Use Plugin

`dsh-mac-cua` is a native macOS plugin for DeepSeek Harness (DSH) that provides a general-purpose Computer Use solution through the Accessibility API. It uses a persistent JavaScript REPL and the `sky` API to allow agents to directly read and operate on desktop elements via code, without relying on predefined UI mappings. Installation requires running a script to configure paths and manually enabling system accessibility and screen recording permissions. Core features include reading application state (with support for incremental diffs and screenshots) and performing actions such as clicking, typing, and dragging. Agents use the `nodeRepl` tool to write JavaScript that calls `sky` methods. This plugin supports macOS