dsh-pin: Add two levels of pinning to DeepSeek Harness sidebar sessions

dsh-pin is a DSH plugin maintained by Yu-tao-Li, designed to optimize the session management experience of the Web GUI sidebar. The plugin adopts a pure client-side architecture with zero runtime dependencies, enhancing the accessibility of frequently used sessions through a two-level pinning feature: 📌 Workspace-local pinning uses the host's official API to persist order, suitable for single workspace management; ⌃⌣ Global pinning area enables cross-workspace quick access, affecting only the display hierarchy and precisely restoring position upon cancellation. The plugin supports pinning multiple sessions simultaneously, level switching, and automatically adapting to different list modes. Installation involves executing specific commands and restarting the service, requiring a Node >=22 environment. While it does not modify the DSH core and offers high security, it is restricted to Web GUI use only and may become ineffective after major version upgrades due to reliance on internal structures. Overall, dsh-pin is designed for high-frequency usage.