dsh-opencode-tui: Reuse the Original opencode TUI Interface for DeepSeek Harness

`dsh-opencode-tui` is a client plugin developed for DeepSeek Harness (DSH), designed to address the absence of a terminal interactive interface in DSH. By running a protocol compatibility layer within the DSH process, the plugin directly reuses opencode's high-quality TUI interface while delegating logic for Agent, session, and tool management to DSH. Its features include UI reuse, logic-driven behavior, protocol compatibility, and storage integration. Developers need to configure parameters such as binary paths and preset IDs. After installation, messages and sessions are automatically saved to DSH storage. When using the plugin, note that it depends on the opencode binary and, due to sandbox pty limitations, the sidebar and some layouts may not render correctly. This plugin enables developers to focus on Agent logic.