Preserve exact frozen music and reranker manifest bytes across checkouts

.gitattributes

@@ -6,3 +6,8 @@
 tools/embeddinggemma2/*.patch -whitespace
 # Frozen quality snapshots must retain exact bytes across operating systems.
 fixtures/mixed/sources/** -text
+
+# Frozen diagnostic manifests/labels retain the exact bytes used in recorded runs.
+fixtures/music-validation-v1/*.json -text
+tools/rerank-eval/*-plan.json -text
+tools/rerank-eval/*-manifest.json -text