Fix #147270: Smooth by angle asset detection broken

Previous attempts:
- 6d884e0da5
- 80e8493c11

It seems `BLI_path_normalize` was doing more than necessary and that
was getting in the way. This PR adds an automated test to avoid the issue
in the future.

Pull Request: https://projects.blender.org/blender/blender/pulls/148069

tests/python/object_edit.py

@@ -0,0 +1,39 @@
+# SPDX-FileCopyrightText: 2025 Blender Authors
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+
+import unittest
+import bpy
+import sys
+
+
+class TestObjectEdit(unittest.TestCase):
+
+    def setUp(self):
+        if bpy.context.object and bpy.context.object.mode != 'OBJECT':
+            bpy.ops.object.mode_set(mode='OBJECT')
+        for mesh in [mesh for mesh in bpy.data.meshes]:
+            bpy.data.meshes.remove(mesh)
+        for ob in [ob for ob in bpy.data.objects]:
+            bpy.data.objects.remove(ob)
+
+    def test_auto_smooth_detection(self):
+        bpy.ops.mesh.primitive_cube_add()
+        ob = bpy.context.object
+        bpy.ops.object.shade_auto_smooth(use_auto_smooth=True)
+        bpy.ops.object.shade_auto_smooth(use_auto_smooth=True)
+        bpy.ops.object.shade_auto_smooth(use_auto_smooth=True)
+        bpy.ops.object.shade_auto_smooth(use_auto_smooth=True)
+        self.assertEqual(len(ob.modifiers), 1)
+        bpy.ops.object.shade_flat()
+        self.assertEqual(len(ob.modifiers), 0)
+        bpy.ops.object.shade_auto_smooth(use_auto_smooth=True)
+        bpy.ops.object.shade_smooth()
+        self.assertEqual(len(ob.modifiers), 0)
+
+
+if __name__ == '__main__':
+    import sys
+    sys.argv = [__file__] + (sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else [])
+    unittest.main()