Freeze actual Google music metadata and precise speech timing diagnostics

tools/media-eval/README.md

@@ -33,3 +33,30 @@ The dense reference samples video every two seconds and PCM in thirty-second win
 - Model agreement with another implementation, synthetic document-seed scores, and this small-media benchmark each answer different questions. None is production quality certification.
 
 Detailed provenance is in [the fixture README](../../fixtures/media/README.md). The final assessment belongs in [MEDIA-QUALITY.md](../../docs/MEDIA-QUALITY.md).
+
+## Music metadata hypothesis diagnostic
+
+`music_metadata` compares raw audio with the per-file maximum over real audio
+and one Google-embedded metadata passage. It has no tuned weight or rejection
+threshold and does not change production. `prepare` freezes actual FFprobe tags,
+source hashes, default production audio windows, and all 65 existing queries
+before inference. Existing plans/reports cannot be overwritten.
+
+```powershell
+cargo test --manifest-path tools/media-eval/Cargo.toml --bin music_metadata --locked
+cargo run --manifest-path tools/media-eval/Cargo.toml --bin music_metadata --locked -- prepare fixtures/media .searchi/media-runtime/bin/ffmpeg.exe .searchi/media-runtime/bin/ffprobe.exe .searchi/qa/music-metadata-v1-plan.json
+$env:SEARCHI_FORCE_CPU = '1'
+cargo run --manifest-path tools/media-eval/Cargo.toml --bin music_metadata --locked -- run fixtures/media .searchi/media-runtime/bin/ffmpeg.exe .searchi/media-runtime/bin/ffprobe.exe .searchi/qa/music-metadata-v1-plan.json .searchi/models/embeddinggemma2 .searchi/runtime/auto/Release/searchi-gemma-worker.exe .searchi/qa/music-metadata-v1-results.json
+```
+
+The whitelist is artist, title, album, genre and composer in that fixed order,
+bounded to 2048 UTF-8 bytes. Missing/blank tags produce no metadata vector;
+encoder, comment, URLs and copyright boilerplate are excluded. Literal misleading
+tags remain misleading evidence: this tool does not verify musical instruments
+or generate a description. Metadata evidence has no invented timestamp.
+
+This is the known two-music-file pool, not mixed production retrieval. Other-file
+positives are explicitly ineligible, filters remain explicitly unsupported, and
+all unfiltered negatives remain visible without abstention. Existing queries are
+diagnostics rather than new held-out evidence. Unseen music with missing and
+misleading tags needs independently frozen validation before deployment.