MM-Fi windows are stride-1 (~99% overlap), so an index-level split leaks; and
bin/train.rs validated real training against a SYNTHETIC val set, making any
printed PCK meaningless on two counts.
- MmFiDataset::subject_disjoint_split partitions whole subjects -> the two views
share no subject and no window (leak-free by construction, deterministic per
seed). assert_split_leak_free verifies subject- AND window-disjointness and is
called inside the split so a leaky split is never handed out.
- bin/train.rs now prefers the real split; the synthetic path is a labelled
run_smoke_test ("[SMOKE-TEST] DO NOT REPORT") reachable only as a fallback.
- New DatasetError::InvalidSplit.
Tests prove disjointness, determinism, single-subject/bad-fraction rejection,
and that the validator catches an injected subject leak.
Co-Authored-By: claude-flow <ruv@ruv.net>
2a2a2c5b06