Evaluate frozen relevance hypothesis once on held-out Google CPU queries

tools/relevance-eval/README.md

@@ -1,10 +1,11 @@
-# Calibration-only relevance diagnostic
+# Frozen relevance diagnostic
 
 This internal runner uses searchi's shared Rust engine and genuine Google
-EmbeddingGemma 2. It has **no held-out execution option**. It indexes all 14 frozen
-source files as the fixed distractor library, but evaluates only the 24
-calibration queries. Held-out queries stay unevaluated until a policy and its
-parameters are frozen using calibration evidence.
+EmbeddingGemma 2. By default it indexes all 14 frozen source files as the fixed
+distractor library and evaluates only the 24 calibration queries. Held-out
+execution requires `--held-out-policy` with the exact SHA-256 of the hypothesis
+frozen in commit `e7245fe`, before held-out inference. Changed policy bytes are
+rejected. The two splits are selected independently and never mixed in one run.
 
 First verify all frozen labels, source bytes, licenses and split integrity:
 
@@ -21,6 +22,14 @@ $env:SEARCHI_FORCE_CPU = '1'
 tools/relevance-eval/target/release/searchi-relevance-eval.exe fixtures/relevance-v2 C:/path/to/verified-models C:/path/to/searchi-gemma-worker.exe .searchi/qa/calibration-v2.json
 ```
 
+For the one frozen held-out evaluation, append
+`--held-out-policy tools/relevance-eval/policies/cosine-v1.json` and use a new
+held-out report name. Raw lexical, semantic and production hybrid results are
+retained. `scores.hypothesis_semantic` evaluates raw semantic candidates after
+the frozen cutoff; it is not a newly executed filtered hybrid fusion. This
+diagnostic does not deploy a threshold into the shared engine. Do not retune
+this policy using the held-out outcomes.
+
 Supply an existing output directory and a new output filename. Existing evidence
 is never overwritten: the output is reserved with `create_new` before costly
 work and subsequent phase/row checkpoints replace JSON atomically. The runner verifies fixture SHA-256, exact source bytes,