dsh-fork-edit: DeepSeek Harness Turn-Level Conversation Editing Plugin

dsh-fork-edit is a DeepSeek Harness plugin designed to address the problem of modifying historical conversations. Instead of writing custom events, it forks a new session at a closed boundary, ensuring the history remains readable and semantically simple. Core features include hover-to-editing for historical user messages, tree-grouped branch lineage in the sidebar, and cascading archiving of subtrees. Technically, it executes transactions through seams in the source agent and automatically rolls back on failure. The plugin has removed the standalone retry entry point, retaining only the `retry-turn` mode of the HTTP API.