usecase-must-be-wired returned {} when the manifest parsed to null,
silently disabling the error-level gate when the manifest existed but
could not be read. It now reports unparseableManifest on Program in
that case; a genuinely missing manifest stays a no-op (that is
feature-must-have-manifest's job).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>