A header cut short raised struct.error, which no caller of
read_gguf_header catches (they skip a model on ValueError or OSError),
so one truncated file escaped the whole preset pass. A short read now
raises ValueError.
The status row sized a side-loaded split by its first file, which can
be a metadata stub of a few MB; it now sums every part on disk. The
split fixture writes model metadata into part 1 only, as gguf-split
does: a published Flash Next split carries 67 keys in part 1 and only
its 3 split.* keys in parts 2-3.
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