Immutable source snapshot

browser-local-cm7-v1 snapshot

CM-7 schema-2 state-input browser integration; FP32 selected update2232 checkpoint 29e68a8e85336cbb1f56efdad36bd76217728b6a376d1e5f74e89887d21383da. ONNX Runtime Web 1.24.3, chess.js 1.4.0. Exact integrated source; standard-game UI, fixed masked120-slot prompt,512 raw output classes. Three-ply browser helper is separate from live seven-ply search. Original UI and terminal PGN export preserved; prototype scorer/codec/worker/runner unchanged except adding PGN export utility.