Record real Google mixed retrieval baseline and remaining quality failures

fixtures/mixed/README.md

@@ -1,7 +1,8 @@
 # Mixed All-files diagnostic v1
 
-This is a frozen, small diagnostic, **not a production quality score**. No mixed
-model run has been performed yet.
+This is a frozen, small diagnostic, **not a production quality score**. The first genuine CPU mixed
+run is recorded in [MIXED-QUALITY.md](../../docs/MIXED-QUALITY.md); its failures
+remain visible and v1 labels remain unchanged.
 
 The corpus contains 32 actual files: six searchi implementations, four searchi
 technical documents, two complete pinned llama.cpp source files, and twenty