DSH Client UI Responsive

Key features

• Same slots, same servicessidebar/conversation/details/shell.overlay and ctx.layout are provided identically to ui-layout — consumers (ui-sidebar, ui-conversation) work unchanged.
• Component specshost CDP against a served page at 412px (drawer open/close, mask) and 1280px (three-column regression) — see the project verification log in the coordination repo.
• Mobile state semanticshamburger toggles the drawer (mask tap closes)
• opening details via ctx.layout.openDetails() shows the bottom sheet
• shell.overlay stays the top layer (z 20).