TestRawHeadingCaseIsFolded does not discriminate the fold it is named for and the entire package stays green when the guard is removed

TestRawHeadingCaseIsFolded does not discriminate the fold it is named for and the entire package stays green when the guard is removed

Found by the round-9 adversarial RUTHLESS review of build/itd-183, by mutation. INTRODUCED BY 2225d6cb.

Replacing strings.EqualFold(rest[m[2]:m[3]], name) at project.go:595 with byte equality leaves the ENTIRE internal/core/reading suite green. All three rows survive for reasons unrelated to folding: the opener capture is now raw (<H2> yields name H2, matching </H2> byte-for-byte), and the soft blank-line bound rescues the mixed-case row -- every row has a blank line after the close.

The guard is nonetheless load-bearing: under the mutant, <h2>Audit Notes</H2> followed by trailing prose with NO blank line leaks end to end, and refuses at HEAD.

This is the fourth mutation-vacuous guard the two reviewers have found across this workstream, and the second found on a test written in the very round that was closing two others. The lesson stands and is now in every builder brief: a test that stays green when its guard is removed is decoration, and the only way to know is to remove the guard.

Remedy: add a row with no blank line between the mixed-case close and the following prose, e.g. <h2>Audit Notes</H2>\nand trailing prose <sentinel>.