dsh-copy-session-ref: Standardized Session Referencing and Context Recall Plugin

The `dsh-copy-session-ref` plugin addresses the lack of a standard reference mechanism in DeepSeek Harness by adding a “Copy Reference” entry to the session row menu and floating card. It generates a standardized `@[name](dsh-session:...)` format, making it easy to paste into the input box to recall context. It supports configurable regex naming rules and provides installation methods for web and desktop.