Headless previews can render draft content, but Canvas currently cannot identify, select, or move components within them. ### Proposed resolution Add component, slot, and region markers to draft output across framework adapters. Measure these boundaries using the same rules as the standard preview and send the resulting rectangles back to Canvas. Keep auto-save refreshes synchronized and provide standard empty drop targets. ### User interface changes Headless previews receive the standard Canvas selection overlays and drag-and-drop behavior.