Local tokenization does not always agree with the input_length the provider
reports, which left the release row carrying a block count derived from our own
count. Truncate or pad digest_hexes to the block count implied by the provider
value. Padding digests are derived per request, so a padded block can never
collide with another request and be scored as shared prefix reuse.
Collapse chunk_*.jsonl in rounds with a bounded merge fan-in so the number of
simultaneously open chunk iterators stays flat regardless of how many chunks a
trace produces, and write a resume manifest so --resume-tmp-dir can continue
from an existing formatter temp directory without rescanning the raw trace.
