dsh-conversation-threads: DSH Dialog Message Bar Navigation Track

`dsh-conversation-threads` is a plugin that adds a Codex-style navigation thread to DSH, helping users quickly locate historical messages in long conversations. The thread appears on the right side of the sidebar, includes short lines corresponding to user messages, and supports hover previews, click-to-jump, and scroll synchronization. The plugin can be installed persistently as a Bundle or activated dynamically as a Skill. It is implemented entirely on the client side and poses no privacy risks.