The source-build pipeline and the binNMU metadata path had drifted into
two inline parsers with different acceptance rules: binary.rs filled
names from any line with a third column but partials only from
exactly-three-column lines, so a 4+ column Checksums line made
&partials[name] panic by map index. Both paths now share one parser
that accepts the modern 3-column and the legacy 5-column Files layout,
rejects anything else with an error naming the field and line, and all
remaining lookups go through .get() with a clear error instead of
indexing. Legacy 5-column Files md5s were previously attributed to the
section token instead of the file name.