Ceremony is a flat repo (#112 D3); changelog.d/135.md, 137.md, 144.md and
151.md landed with a '### Fixed'/'### Changed' heading, each individually
legal to changelog_fragment_problem, and together they made the directory
mixed-shape — 'bin/changelog-assemble 0.3.0 --check' refused on main.
Delete the heading line and its following blank line from each; every
bullet stays byte-identical (#157 D1). No fragment for this PR: its whole
diff is unpublished fragment text (#157 D2).
Closes#158
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>