refactor(editor): delete curving + endpoint reshaping flags

Migrate `curvingWall`, `curvingFence`, `movingWallEndpoint`, `movingFenceEndpoint`
(and their setters) off `useEditor` onto the authoritative interaction scope.
The `reshaping` scope variant gains an `endpoint` discriminator; existence
checks read `useIsCurveReshape()` / `useEndpointReshape()`, and the few sites
that need the node (affordance-tool mounts, wall-vs-fence type checks) read it
from `useReshapingNode()` — a frozen drag-start snapshot, mirroring the old
flags so the tools' own per-frame writes don't feed back. `MovingWallEndpoint`
/ `MovingFenceEndpoint` move to the kind-owned tools that consume them.

`editor-api` is simpler: endpoint engagement is kind-agnostic, and the
`engageMove` reshape clears are gone (the scope is single-owner).

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

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

@@ -19,7 +19,7 @@ import {
   snapBuildingLocalToWorldGrid,
   snapScalarToGrid,
   triggerSFX,
-  useEditor,
+  useInteractionScope,
 } from '@pascal-app/editor'
 import { useViewer } from '@pascal-app/viewer'
 import { useCallback, useEffect, useRef, useState } from 'react'
@@ -47,7 +47,9 @@ export const CurveWallTool: React.FC<{ node: WallNode }> = ({ node }) => {
   ])
 
   const exitCurveMode = useCallback(() => {
-    useEditor.getState().setCurvingWall(null)
+    useInteractionScope
+      .getState()
+      .endIf((scope) => scope.kind === 'reshaping' && scope.reshape === 'curve')
   }, [])
 
   useEffect(() => {