dsh-session-xc: A Session Management Enhancement Plugin for DeepSeek Harness

The `dsh-session-xc` plugin is designed to address the low efficiency of sidebar management in DeepSeek Harness (DSH). It provides features such as session count statistics, archive management, cross-workspace drag-and-drop handoff, active session filtering, and automatic naming for new sessions. The plugin supports installation via CLI, requires a restart to take effect, and offers multiple toggle settings. Note that it requires DSH 0.1.7 or later, automatic naming only works for unofficial model routing, and moving pinned sessions may require a restart to complete the file transfer.