D7 mirroring candidate (a)/(i) `unquote_scalar`, measured. The sibling grew that
function after a duplicated conversion had drifted; our counterpart
`okf._strip_matching_quotes` is genuinely ONE rule -- one definition, one call
site, and `unquote` appears in 0 of 76 .py files under src+tests (positive
control: the same query finds `parse_frontmatter`). So the drift shape is absent.
But the rule was covered only at its edge. Detaching it outright is red; each of
its three clauses was green-but-dead against the whole 950-test suite -- weakening
the length guard, dropping the matching requirement, and widening the quote set
with a symmetric delimiter all left the suite green. Same class as the
_STRUCTURE_MARKERS hole: named and edge-covered is not covered.
tests/test_okf_unquote_loadbearing.py closes the three clauses (950 -> 955). Each
clause test is green before and red after exactly its own mutation, with the
population control green in both, clause 3 pinned on its line via --red-at.
A measuring trap, measured: the first clause-3 mutation added '[' to the quote
set and the suite stayed green -- which reads as "not covered" but is a NO-OP,
since '[' can never satisfy the matching clause. Flow-form values are protected
by the matching clause, not the quote set. The harness cannot distinguish a
behaviour-preserving mutation from an undetected seam; both surface as "stayed
GREEN". A mutation must be shown to change behaviour before its green is read as
a hole.
No flow decoding is added here -- that is the sibling's B4 work, and these tests
pin today's boundary so it cannot land silently on this side.
Co-Authored-By: Claude <claude-opus-5>
Kjell Tore Guttormsen
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