dsh-terminal-manager: DSH Multi-Session Terminal and Agent Tooling Plugin

`dsh-terminal-manager` is a client-side terminal management plugin for the DSH ecosystem. It supports multi-session management over SSH and Telnet, and can embed terminal capabilities into the Agent tool surface and the workspace UI. Built on a web platform, it depends on React 18 and DSH core components, and its source code can be obtained from its GitHub repository. Developers should review the source code and the contents of the LICENSE file before use.