* M12: boards dot grid, re-attaching connector ends, curved connectors
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.
* M12: boards dot grid: blending a dot in a function of its own (Sonar)
Board files (File > New board) with sticky notes, shapes with text, connectors that follow what they join (straight or elbow, arrowheads, labels), marker, highlighter and eraser, and stamps; a board toolbar and a contextual bar; the Design panel hidden on boards, Prototype and Dev Mode refused there. Boards are ordinary FigCraft files built from ordinary layers, so saving, undo, export, MCP and live sessions work unchanged. File tabs, recent files and Open files show a pen nib for design files and a note for boards (original icons drawn in code).