The norms guard was the tautology `n.len() == n.len()`, so a norms dataset
of any length was trusted and corrupted every cosine score; other per-record
datasets were not length-checked at all, so a truncated file loaded and then
panicked on the first index. Mismatches are now MemoryError::Schema, stored
norms are used only when they match the record count, and embedding_dim == 0
with records present is rejected instead of panicking in chunks(0).
Co-Authored-By: Claude Fable 5.1 <[email protected]>
