openstetho v0.4.0-murmur-ensemble — clean 3-seed ensemble (5s)

Clean public-data murmur model upgrade: a 3-seed bagged CNN+BiGRU ensemble (5 s / 78-frame), shipped as one fused Core ML package.

Model: transferred best-F1 0.5972 → 0.6439, OoF AUROC 0.8172 → 0.8415, Platt ECE 0.040 → 0.019 (5-fold patient-level CV, gate-verified). No teacher distillation.

Operating point: Youden default, sensitivity 0.724 / specificity 0.829 (screening-leaning); metadata-tunable.

Asset MurmurCNN.mlpackage.zip bundles:

• MurmurCNN.mlpackage — fused 3-model probability-mean ensemble (5 s / 78-frame), sidecar n_frames:78, murmur_threshold:0.535999.
• S3CNN_v2.mlpackage — unchanged from v0.3.1.

stetho-ui auto-upgrades via /releases/latest/download/; the engine reads window length + threshold from the sidecar metadata.

See PR #1 for the regression-gate harness and full provenance.