parseManifestUseCases returning null for a manifest that exists made
the cross-feature gate silently skip that feature. findUnparseableManifests
now runs before the empty-graph early exit (an unparseable manifest
contributes zero events and would otherwise pass as nothing-to-check)
and any hit fails the run. Reader-closure from the downstream fork is
not ported: this tree has no reads: manifests or ./reader exports yet.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
