Map RNA float array properties to mathutils types using subtype

RNA properties with subtypes like TRANSLATION, XYZ, EULER, QUATERNION,
COLOR, MATRIX are now mapped to the corresponding mathutils types
(Vector, Euler, Quaternion, Color, Matrix) instead of list[float].

Also:
- Add gpu.types override for 5.1 (uniform_float accepts mathutils types)
- Fix README snippet to use assert for active_object None check

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

overrides/5.1/gpu.types.json

@@ -0,0 +1,7 @@
+{
+  "GPUShader.uniform_float": {
+    "params": {
+      "value": "float | int | Sequence[float] | mathutils.Matrix | mathutils.Vector | mathutils.Euler | mathutils.Quaternion | mathutils.Color"
+    }
+  }
+}