Add SimpleHands asset with WhiteHand prefab

Imported third-party stylized hand asset; provides the WhiteHand rig
used by the finger IK system.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/SimpleHands/Textures.meta

@@ -0,0 +1,8 @@
+fileFormatVersion: 2
+guid: 6302c9b39a34a46cea4828af8ae53a36
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: