DeepSeek Harness Plugin: dsh-connection-card-host

`dsh-connection-card-host` is a plugin built for DSH to address the lack of a programmatic management layer in multi-session collaborative workflows. It elevates “connections” to first-class citizens and, by defining sessions as nodes, connections as containers, and cards as scopes, provides flexible permission boundaries and resource management for interactions between sessions. The plugin supports multiple interaction modes: automatically pulling the counterpart’s state to enable mutual “seeing” and “conversation,” using mounted “cards” to share tools and dependencies, and providing a “convention box” to manage consensus. Its core mechanism is pull-based awareness, which incurs overhead only when the other side actively queries, enabling efficient isolated collaboration without interrupting sessions.