DeepSeek harness client

Key features

• Seamless window (fully self-drawn title bar): completely abandon the original title bar (frame: false), the title bar and the sidebar are of the same color, and are connected to form an L-shaped overall surface
• Node.js (including npm/npx, dsh relies on the system Node to run and needs to be found by where node)
• File/Edit/View/Window/Help plain text menu is directly embedded in the title bar, with self-drawn minimize/maximize/close keys in the upper right corner
• The content area is a "floating card" with rounded corners in the upper left corner, slightly brighter, and the color of the bottom surface shows through the rounded corner gap
• The background color of the title bar/sidebar switches in real time following the theme (light/dark), creating a seamless look and feel.