dsh-recall-plugin: Recall Files and Conversations Together Before Message Delivery

dsh-recall-plugin adds a '↶ Recall' button next to DSH user messages. Upon confirmation, the workspace files are restored via an independent shadow git snapshot, and the conversation history is reverted to before the message was sent using sessions.fork. The original session is archived and can be recovered. It does not affect the project's own git; snapshots are stored in $DSH_HOME, supporting exclusion lists, tree-structured snapshot management, and self-healing. Requires git CLI and DSH 0.1.0-rc.x. Installation command: dsh plugin --profile web add dsh-recall-plugin.