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>
