feat(editor): node-declared per-context snapping + contextual HUD + painter scope

Generify the snapping/modifier HUD off the FSM scope and node declarations
instead of wall-creation-shaped, leaking pills.

- Per-context snapping (`snappingModeByContext`, persisted): wall / item /
  polygon mode-sets with exclusive modes (grid | lines | angles | off), each
  doing exactly what its chip says. Context is node-declared via the new
  `NodeDefinition.snapProfile` ('item' | 'structural'); the resolver maps
  (profile × action) → context with no per-kind switch.
- Scope-driven HUD: helper-manager reads the interaction scope; reshaping
  (endpoint/curve/boundary) and item move get their own chip, no select-hint
  leak. Rotate R/T rounds to 45°; Alt = force-place only (hidden for
  structural kinds); Shift = cycle everywhere.
- Slab/ceiling drafting: Shift=cycle, mode-aware grid/angle, Enter finishes
  (minDraftVertices); polygon boundary vertex/edge drag begins a reshaping
  scope. Fix grid/angle being ignored on boundary edit + slab creation:
  make resolveSurfacePlanPointSnap exclusive (alignment gated on magnetic) so
  grid/angles keep the snapped fallback instead of the raw cursor.
- Painter application scope: node-derived (single/object/matching/room) from
  the hovered node, cyclable via Shift, single-source HUD chip.
- Remove the redundant GridSnapControl from view-toggles (grid step lives in
  the contextual HUD now).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/nodes/src/wall/curve-tool.tsx

@@ -27,8 +27,8 @@ import { useCallback, useEffect, useRef, useState } from 'react'
 /**
  * Phase 5 Stage D — wall curve tool (kind-owned).
  *
- * 1:1 port of the legacy `CurveWallTool`. Same snap pipeline, Shift
- * override, history dance, activation grace. The wall variant uses
+ * 1:1 port of the legacy `CurveWallTool`. Same snap pipeline,
+ * history dance, activation grace. The wall variant uses
  * `useScene.temporal.getState().pause()` / `.resume()` directly rather
  * than the depth-counted `pauseSceneHistory` helpers — matches legacy.
  */
@@ -36,7 +36,6 @@ export const CurveWallTool: React.FC<{ node: WallNode }> = ({ node }) => {
   const activatedAtRef = useRef<number>(Date.now())
   const originalCurveOffsetRef = useRef(getClampedWallCurveOffset(node))
   const previousCurveOffsetRef = useRef<number | null>(null)
-  const shiftPressedRef = useRef(false)
   const previewOffsetRef = useRef<number>(originalCurveOffsetRef.current)
 
   const initialHandle = getWallMidpointHandlePoint(node)
@@ -87,14 +86,14 @@ export const CurveWallTool: React.FC<{ node: WallNode }> = ({ node }) => {
     }
 
     const onGridMove = (event: GridEvent) => {
-      const bypassSnap = shiftPressedRef.current || event.nativeEvent?.shiftKey === true
       const snapStep = getSegmentGridStep()
       // Snap the cursor on the WORLD XZ grid (still in building-local
       // coords for the rest of the math) so a rotated building doesn't
       // pull the curve handle off the visible grid lines.
-      const [snappedLocalX, snappedLocalZ] = bypassSnap
-        ? [event.localPosition[0], event.localPosition[2]]
-        : snapBuildingLocalToWorldGrid([event.localPosition[0], event.localPosition[2]], snapStep)
+      const [snappedLocalX, snappedLocalZ] = snapBuildingLocalToWorldGrid(
+        [event.localPosition[0], event.localPosition[2]],
+        snapStep,
+      )
       const localX = snappedLocalX
       const localZ = snappedLocalZ
 
@@ -102,16 +101,13 @@ export const CurveWallTool: React.FC<{ node: WallNode }> = ({ node }) => {
         (localX - chord.midpoint.x) * chord.normal.x +
         (localZ - chord.midpoint.y) * chord.normal.y
       )
-      const snappedOffset = bypassSnap
-        ? offsetFromMidpoint
-        : snapScalarToGrid(offsetFromMidpoint, snapStep)
+      const snappedOffset = snapScalarToGrid(offsetFromMidpoint, snapStep)
       const nextCurveOffset = normalizeWallCurveOffset(
         node,
         Math.max(-maxCurveOffset, Math.min(maxCurveOffset, snappedOffset)),
       )
 
       if (
-        !bypassSnap &&
         previousCurveOffsetRef.current !== null &&
         nextCurveOffset !== previousCurveOffsetRef.current
       ) {
@@ -157,23 +153,9 @@ export const CurveWallTool: React.FC<{ node: WallNode }> = ({ node }) => {
       exitCurveMode()
     }
 
-    const onKeyDown = (event: KeyboardEvent) => {
-      if (event.key === 'Shift') {
-        shiftPressedRef.current = true
-      }
-    }
-
-    const onKeyUp = (event: KeyboardEvent) => {
-      if (event.key === 'Shift') {
-        shiftPressedRef.current = false
-      }
-    }
-
     emitter.on('grid:move', onGridMove)
     emitter.on('grid:click', onGridClick)
     emitter.on('tool:cancel', onCancel)
-    window.addEventListener('keydown', onKeyDown)
-    window.addEventListener('keyup', onKeyUp)
 
     return () => {
       if (!wasCommitted) {
@@ -183,8 +165,6 @@ export const CurveWallTool: React.FC<{ node: WallNode }> = ({ node }) => {
       emitter.off('grid:move', onGridMove)
       emitter.off('grid:click', onGridClick)
       emitter.off('tool:cancel', onCancel)
-      window.removeEventListener('keydown', onKeyDown)
-      window.removeEventListener('keyup', onKeyUp)
     }
   }, [exitCurveMode, node])