Restructure to MODEL_SPEC.md convention

.gitattributes

@@ -36,3 +36,5 @@ saved_model/**/* filter=lfs diff=lfs merge=lfs -text
 tokenizer.json filter=lfs diff=lfs merge=lfs -text
 original/phi-4-mini_bf16.pte filter=lfs diff=lfs merge=lfs -text
 quantized/phi-4-mini_8da4w.pte filter=lfs diff=lfs merge=lfs -text
+xnnpack/phi_4_mini_xnnpack_bf16.pte filter=lfs diff=lfs merge=lfs -text
+xnnpack/phi_4_mini_xnnpack_8da4w.pte filter=lfs diff=lfs merge=lfs -text