gh returning nothing left the rollup KEY absent, which collapsed into the same
NONE as a PR that genuinely has no checks -- so an API hiccup presented as
mergeable-by-a-human. That is the unknown-certified-as-green shape this machine
exists to stop, surviving in the one place the #136 fix did not look.
checks_state now reports UNREADABLE for an absent key, and the sweep leaves
that PR exactly as it is rather than recomputing on facts it did not read.
Blocking on it instead would flap the whole board on one bad call.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>