dsh-thread-tools: Cross-Session Tools for DeepSeek Harness

DeepSeek Harness sessions are natively isolated from one another. The `dsh-thread-tools` plugin addresses this collaboration challenge by providing cross-session operation tools. Maintained by wig123, it supports core features such as listing, searching, sending messages, replying, and creating or branching sessions. It enables an active session to send messages to other sessions and read their replies, filling the gap in top-level DSH session interaction. Installation is required via NPM or GitHub source code, with attention to active-state limits, search dependencies, and conditional restrictions on forking.