Migrate roof/stair/elevator draft tools + the 2D floorplan move overlay off the
legacy Shift/Alt=bypass model onto mode-driven snapping (isGridSnapActive /
isMagneticSnapActive); Alt dropped (no validity gate). stair/elevator now use the
live grid step.
These three are placed as footprints, not directional draws, so the angle-lock
mode was meaningless: add NodeDefinition.snapDraftDirectional (default true; false
for roof/stair/elevator) so their draft resolves to the no-angle 'polygon' context
(grid / lines / off). snapContextOf takes an injected draftDirectionalOf, like
profileOf. Add toolHints to stair/elevator so they route through the contextual
HUD and show the snapping chip. Fix one stale Alt-bypass comment in the item
placement coordinator (#9: already force-only). +snapping-mode test.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
