TEST-ONLY: seed the current selection (and active tooth) so selection-scoped
setters (applyToSelected, e.g. setOrtho*ForSelection) act on a known set
without a live grid. Vivifies a defaultState() for any unseen tooth, like
the real selection path. Not part of the public API.
TEST-ONLY: seed the current selection (and active tooth) so selection-scoped setters (
applyToSelected, e.g.setOrtho*ForSelection) act on a known set without a live grid. Vivifies adefaultState()for any unseen tooth, like the real selection path. Not part of the public API.