Update markdown preview test loader for spatial helpers

tests/test_markdown_preview.py

@@ -57,7 +57,12 @@ def _load_preview_functions():
     source = app_path.read_text(encoding="utf-8")
     module = ast.parse(source, filename=str(app_path))
 
-    wanted = {"_to_mathml", "to_math_html"}
+    wanted = {
+        "_to_mathml",
+        "_inject_spatial_gap_placeholders",
+        "_restore_spatial_gap_placeholders",
+        "to_math_html",
+    }
     fn_nodes = [n for n in module.body if isinstance(n, ast.FunctionDef) and n.name in wanted]
     fn_nodes.sort(key=lambda n: n.lineno)