fix(cad): PlateCurved bbox + Surface render under adacpp (full parity)

- _calc_bbox_of_plate_curved: a PlateCurved wraps a face produced externally
  by OCC (loft tool / gxml AdvancedFace import). Under adacpp that raw OCC
  face isn't a native handle — adopt it across the kernel boundary
  (from_topods_pointer, same OCCT version) before querying backend.bbox.
- test_surface_renders_as_face: introspect the result via
  active_backend().faces() instead of a raw OCC TopExp_Explorer, so the
  assertion holds under either backend.

Closes the last geometry-parity gap: every core geometry test passing under
OccBackend now also passes under adacpp (663 vs OCC 655; remaining adacpp
deltas are a hardcoded OCC-mesher vertex-count fingerprint and a dev-link
kaleido PATH artifact — neither a geometry-parity issue). OccBackend
unchanged (655).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: Krande

src/ada/api/bounding_box.py

@@ -100,14 +100,21 @@ def _calc_bbox_of_plate_curved(self) -> tuple[tuple, tuple]:
         """
         from ada.cad import active_backend
 
+        backend = active_backend()
+
         # Use the bare face (no extrusion) so the bbox isn't padded by
         # the prism thickness on whichever axis the normal points.
         # solid_occ returns the face for the raw-OCC path and the
         # AdvancedFace→OCC for the Geometry-backed path. optimal=False +
         # use_mesh reproduces the prior brepbndlib.Add(face, bbox) exactly.
-        xmin, ymin, zmin, xmax, ymax, zmax = active_backend().bbox(
-            self.parent.solid_occ(), optimal=False, use_mesh=True
-        )
+        shape = self.parent.solid_occ()
+        # PlateCurved wraps a face produced externally by OCC (loft tool /
+        # gxml AdvancedFace import). Under a non-OCC backend that raw OCC face
+        # isn't a native handle yet — adopt it across the kernel boundary
+        # (same OCCT version → safe) before querying the backend.
+        if not backend.is_handle(shape):
+            shape = backend.adopt_occ_shape(shape)
+        xmin, ymin, zmin, xmax, ymax, zmax = backend.bbox(shape, optimal=False, use_mesh=True)
         return (xmin, ymin, zmin), (xmax, ymax, zmax)
 
     def _calc_bbox_of_plate(self) -> tuple[tuple, tuple]:

tests/core/api/plates/test_plate_curved.py

@@ -189,10 +189,11 @@ def test_surface_renders_as_face_not_extruded_prism():
     occ_shape = surf.solid_occ()
     assert occ_shape is not None
     # The shape should be a face (or compound with a face), not a
-    # zero-volume prism. We just check it's not the placeholder None.
-    from OCC.Core.TopAbs import TopAbs_FACE
-    from OCC.Core.TopExp import TopExp_Explorer
-    assert TopExp_Explorer(occ_shape, TopAbs_FACE).More()
+    # zero-volume prism. Introspect via the active CAD backend so this
+    # holds under either backend (pythonocc or adacpp).
+    from ada.cad import active_backend
+
+    assert len(active_backend().faces(occ_shape)) >= 1
 
 
 def test_surface_curved_inherits_plate_curved_handling():