Phase 5 Stage D wall: port CurveWallTool to DragAction (first wall D)

Direct copy of the fence curve recipe — pure
`curveWallDragAction` (chord-perpendicular projection + clamp +
normalize + single-undo dance) plus a thin wrapper feeding
`useDragAction`. Mounted via `def.affordanceTools.curve`.

Slight precision difference vs legacy: the legacy CurveWallTool snapped
the pointer position to `getWallGridStep()` before projecting onto the
chord normal; the ported action skips that pre-snap and relies on
`normalizeWallCurveOffset` to settle the final value. The user-visible
result is the same magnitude of step, just with the snap applied at
the offset level instead of the position level.

Remaining wall D affordances (endpoint move, whole-wall move,
placement) are larger and queued for future sessions — wall's move
tool alone is 804 LoC with the linked-wall corner-cascade logic.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -0,0 +1,62 @@
+'use client'
+
+import { getWallMidpointHandlePoint, useScene, type WallNode } from '@pascal-app/core'
+import { CursorSphere, triggerSFX, useDragAction, useEditor } from '@pascal-app/editor'
+import { useViewer } from '@pascal-app/viewer'
+import { useEffect, useState } from 'react'
+import { curveWallDragAction } from './actions/curve'
+
+/**
+ * Phase 5 Stage D — thin React wrapper around `curveWallDragAction`.
+ *
+ * Replaces the legacy `CurveWallTool` (178 LoC). Same UX as the fence
+ * curve port — cursor sphere follows the chord-perpendicular projection
+ * of the pointer, dragging the wall's `curveOffset` live; grid:click
+ * commits with the single-undo dance, Esc cancels.
+ *
+ * Mounted by ToolManager via `def.affordanceTools.curve` when
+ * `useEditor.curvingWall` activates.
+ */
+export const WallCurveTool: React.FC<{ node: WallNode }> = ({ node }) => {
+  const initialHandle = getWallMidpointHandlePoint(node)
+  const [cursorPos, setCursorPos] = useState<[number, number, number]>([
+    initialHandle.x,
+    0,
+    initialHandle.y,
+  ])
+
+  const exitCurveMode = (committed: boolean) => {
+    if (committed) triggerSFX('sfx:item-place')
+    useViewer.getState().setSelection({ selectedIds: [node.id] })
+    useEditor.getState().setCurvingWall(null)
+  }
+
+  useDragAction({
+    active: true,
+    action: curveWallDragAction,
+    initial: {
+      node,
+      point: [initialHandle.x, initialHandle.y],
+    },
+    onCommit: () => exitCurveMode(true),
+    onCancel: () => exitCurveMode(false),
+  })
+
+  const liveCurveOffset = useScene((s) => {
+    const live = s.nodes[node.id]
+    return live?.type === 'wall' ? ((live as WallNode).curveOffset ?? 0) : 0
+  })
+
+  useEffect(() => {
+    const handlePoint = getWallMidpointHandlePoint({ ...node, curveOffset: liveCurveOffset })
+    setCursorPos([handlePoint.x, 0, handlePoint.y])
+  }, [liveCurveOffset, node])
+
+  return (
+    <group>
+      <CursorSphere position={cursorPos} showTooltip={false} />
+    </group>
+  )
+}
+
+export default WallCurveTool