Scoped to the fixtures the new rule actually binds: a fragment whose
predicate complaint is already its name, a smuggled heading, a dangling
heading or the 300-character bound is left alone, so the diagnosis it
tests is still the one it draws. The section-predicate fixtures are
untouched (D4).
The computed-length fixtures keep their measured lengths: the cite is
seven characters, so an entry that must measure exactly 300 builds 293
of the run and lets the cite carry the rest. 33.md's cite lands on the
last continuation line, which is the wrapped-citation case.
Refs #262
'- Fixed entry.' is shared between the dangling-heading fragment fixture
and the section-predicate fixture, so the global replace crossed D4's
line. Next commit filters to fragments that actually red on the cite rule.
Refs #262
