Group API

Group accepts x, y, width, height, minimum dimensions, resize handle configuration, metadata, callbacks, groupCallbacks, canContain, and edgePan.

Use title for a text header or headerContent for a custom snippet. The header is the move surface; the group body remains pointer-transparent so member nodes receive input.

onMembershipChange and onGeometryCommit are convenience callbacks composed with their callback-object equivalents. getNodeObject() returns the core group.