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/Demo/SimpleHands.unity.meta

@@ -0,0 +1,14 @@
+fileFormatVersion: 2
+guid: cddec4710686f41f7beaf4c5498d7775
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
+AssetOrigin:
+  serializedVersion: 1
+  productId: 221297
+  packageName: Stylized - Simple Hands
+  packageVersion: 1.0
+  assetPath: Assets/SimpleHands/Demo/SimpleHands.unity
+  uploadId: 497294