Board pages draw a dot grid in the canvas render, after the page colour
and under the layers (figcraft_render::Dots), thinned out when zoomed out
and coloured from the theme's ink against the page. A selected connector
shows its ends as handles; dragging one onto an object re-attaches it,
onto empty canvas leaves it free (board.reattach, one undo step, also
over MCP). Connectors can be curved, and elbows go around the objects
they join when the short way would cross them.