feat(nodes): mode-aware roof-segment edit + 2D rotation parity with 3D

Roof-segment edit/move ignored the active snap mode and showed no chip:
- add snapProfile:'structural' so a body-move resolves the no-angle polygon
  context (grid/lines/off) like every other structural move;
- resize uses getSegmentGridStep() (0 outside grid mode = the "smooth" resize
  that used to need a held Shift), dropping the captured gridSnapStep + Shift;
- move drops its Shift bypass;
- the affordance dispatcher opens a boundary reshape scope for the resize so
  the snapping chip shows and the context resolves.

2D rotation handles now match the 3D gizmo across all six rotate affordances
(column / elevator / roof-segment / shelf / spawn / stair): a shared
rotateAffordanceDelta snaps to the 15° step unless Shift (free), the
dispatcher opens the same ROTATE_HANDLE_DRAG_LABEL handle-drag scope the 3D
gizmo uses so the contextual HUD shows the "Shift = rotate freely" hint, and
the live degree readout snaps to match the committed rotation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/nodes/src/elevator/floorplan-affordances.ts

@@ -4,6 +4,7 @@ import {
   type FloorplanAffordance,
   useScene,
 } from '@pascal-app/core'
+import { rotateAffordanceDelta } from '../shared/rotate-affordance'
 
 const MIN_ELEVATOR_DIM = 0.6
 
@@ -83,11 +84,13 @@ export const elevatorRotateAffordance: FloorplanAffordance<ElevatorNode> = {
 
     return {
       affectedIds: [elevatorId],
-      apply({ planPoint }) {
-        const currentAngle = Math.atan2(planPoint[1] - cz, planPoint[0] - cx)
-        let delta = currentAngle - initialAngle
-        while (delta > Math.PI) delta -= 2 * Math.PI
-        while (delta < -Math.PI) delta += 2 * Math.PI
+      apply({ planPoint, modifiers }) {
+        const delta = rotateAffordanceDelta({
+          center: [cx, cz],
+          initialAngle,
+          planPoint,
+          free: modifiers.shiftKey,
+        })
         const newRotation = initialRotation - delta
         lastRotation = newRotation
         useScene.getState().updateNode(elevatorId, { rotation: newRotation })