chore: switch binary tracking from LFS to Xet for HuggingFace

Update .gitattributes to use filter=xet for *.png, *.jpg, *.jpeg,
*.wav, *.mp3, *.gif, *.webp — required by HuggingFace Spaces which
uses Xet storage instead of Git LFS.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitattributes

@@ -1,3 +1,10 @@
+*.png filter=xet diff=xet merge=xet -text
+*.jpg filter=xet diff=xet merge=xet -text
+*.jpeg filter=xet diff=xet merge=xet -text
+*.wav filter=xet diff=xet merge=xet -text
+*.mp3 filter=xet diff=xet merge=xet -text
+*.gif filter=xet diff=xet merge=xet -text
+*.webp filter=xet diff=xet merge=xet -text
 *.png filter=lfs diff=lfs merge=lfs -text
 *.jpg filter=lfs diff=lfs merge=lfs -text
 *.jpeg filter=lfs diff=lfs merge=lfs -text