dsh-conversation-links: Carry over DSH conversation records to another conversation

The DSH client plugin maintained by Penguin-SAMA provides cross-conversation referencing features: referencing other conversations via `@` in the input box, dragging conversations from the sidebar to the input box, and inserting messages into another conversation by checking them in the selection panel. It registers its own `@conversation-link` source and reads the client's session list directly, avoiding the issues where DSH's built-in `@` source silently degrades to an empty array or loses conversation grouping when remote errors occur. The reference format is consistent with DSH's built-in citations, while snapshot injection is still handled by DSH's native capabilities. This article provides the installation command (`plugin_manager action=install_bundle`, where `target` is an absolute path to the package directory or `node_modules`), three usage methods, applicable scenarios, and precautions.