dsh-call-session: DeepSeek Harness Cross-Session Communication and Shared Blackboard Plugin

dsh-call-session is an in-process cross-session communication and workspace sharing plugin for DeepSeek Harness, designed to address multi-session collaboration challenges. It provides unicast communication between sessions, shared blackboard storage, and session topology visualization, supporting task handoff, state publishing, and session creation through tools. The plugin is built in by default and easy to install, making it suitable for multi-session scenarios that require long-term coordination or sharing large results. However, for one-off tasks, it is recommended to prefer the built-in subagent.