dsh-chat-gutter: Dual-sided Marker Bands and Quick Navigation in the Chat Area

dsh-chat-gutter is a pure client-side plugin for DSH maintained by lin114514-desng (v0.2.29, MIT license). It draws turn number markers, process badges, and response segment arcs on both sides of the chat column, and provides a two-column "Quick Move" panel in the input area that allows navigation categorized by AI questions, tools, AI responses, and user messages. It does not read session data or modify the official DOM structure. The configuration includes a master toggle for the marker band and highlighting of response start points. For installation instructions, see INSTALL-PLAN.md. Requires DSH >= 0.2.1-rc.2.