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/editor/src/components/tools/tool-manager.tsx

@@ -244,7 +244,17 @@ export const ToolManager: React.FC = () => {
               <MoveFenceEndpointTool target={movingFenceEndpoint} />
             )
           })()}
-        {curvingWall && <CurveWallTool node={curvingWall} />}
+        {curvingWall &&
+          (() => {
+            const Registry = getRegistryAffordanceTool(curvingWall.type, 'curve')
+            return Registry ? (
+              <Suspense fallback={null}>
+                <Registry node={curvingWall} />
+              </Suspense>
+            ) : (
+              <CurveWallTool node={curvingWall} />
+            )
+          })()}
         {curvingFence &&
           (() => {
             const RegistryAffordance = getRegistryAffordanceTool(curvingFence.type, 'curve')