dsh-session-bridge: Session-Level Multithread Orchestration for DeepSeek Harness

`dsh-session-bridge` is a plugin in the DeepSeek Harness (DSH) ecosystem, designed to address limitations of native DSH in maintaining multi-session context. Through a global tool interface, it supports cross-session scheduling and communication. Core features include: 1. **session_create**: creates a regular sub-session in the workspace bound to the current orchestration. 2. **session_send**: supports both queue (FIFO) and interrupt modes for sending messages to a specified session, automatically handling cold starts. 3. **session_list**: enumerates information about regular sessions in the workspace. The plugin only supports operating regular sessions and cannot access sessions owned by sub-agents. All cross-session messages include source-tracing tags. The installation command is `