Fix mypy compatibility and add 5.0 conformance tests

- Qualify bare "object" as builtins.object in bpy.types to avoid shadowing
  by Context.object and similar properties
- Use _Sequence alias import to fix mypy "collections.abc.Sequence not defined"
- Filter out variables that clash with submodule re-exports (e.g. bpy.app)
- Add 5.0 conformance tests from Blender 5.0 mathutils documentation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

conformance/5.0/test_mathutils.py

@@ -0,0 +1,18 @@
+import mathutils
+from math import radians
+
+vec = mathutils.Vector((1.0, 2.0, 3.0))
+
+mat_rot = mathutils.Matrix.Rotation(radians(90.0), 4, "X")
+mat_trans = mathutils.Matrix.Translation(vec)
+
+mat = mat_trans @ mat_rot
+mat.invert()
+
+mat3 = mat.to_3x3()
+quat1 = mat.to_quaternion()
+quat2 = mat3.to_quaternion()
+
+quat_diff = quat1.rotation_difference(quat2)
+
+print(quat_diff.angle)