Blender createObject: pin whitespace meshType refusal, document meshType and null objectType

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

surfaces/blender/docs/install.md

@@ -120,7 +120,8 @@ gets a `failed` receipt whose message names the rule):
 - `createObject`: optional `objectType` (`MESH`, `LIGHT`, `CAMERA`, `EMPTY`; default `EMPTY`),
   `name`, `location`. Any other `objectType` (for example `TEXT` or `CURVE`) is refused with
   the allowed set named. A `MESH` is a cube (`size`); a `meshType` other than `CUBE`
-  (case-insensitive) is refused rather than ignored.
+  (case-insensitive, no surrounding whitespace) is refused rather than ignored.
+  `meshType` is checked only when `objectType` is `MESH`; an explicit `objectType: null` is refused.
 - `importGltf`: `filepath`, `.gltf` or `.glb`, relative to the add-on preference
   `Import Directory` (absolute paths, `..` and symlinks that resolve outside it are
   refused). Empty `Import Directory` disables the action. Needs Blender's glTF add-on.
@@ -159,7 +160,7 @@ gets a `failed` receipt whose message names the rule):
   camera, file path and format are restored after the render. The render blocks
   Blender's UI until it finishes. In a background (`-b`) Blender on Linux, the GL
   engines `BLENDER_WORKBENCH`, `BLENDER_EEVEE` and `BLENDER_EEVEE_NEXT` are refused
-  with a `failed` receipt when `libEGL.so.1` cannot be loaded (probed once), because
+  with a `failed` receipt when `libEGL.so.1` cannot be loaded (probed once and cached for the life of the process), because
   rendering would abort the whole process with no receipt; `CYCLES` renders on the
   CPU. The check applies to the scene's engine when `engine` is omitted. No such
   check runs on Windows or macOS.

surfaces/blender/tests/test_scene_actions.py

@@ -397,7 +397,7 @@ class ActionTests(unittest.TestCase):
         self.assertEqual(self.bpy.created, [])
 
     def test_create_object_refuses_a_mesh_type_other_than_cube(self):
-        for mesh_type in ("CYLINDER", "", 1):
+        for mesh_type in ("CYLINDER", "", 1, " CUBE", "CUBE "):
             receipt = self.run_action(action="createObject", objectType="MESH", meshType=mesh_type)
             self.assertEqual(receipt["status"], "failed", mesh_type)
             self.assertIn("CUBE", receipt["message"])