When `gh pr view` failed, the fallback left the `statusCheckRollup` key
absent, and `(.statusCheckRollup // [])` collapsed that into the same
NONE as a PR with genuinely no checks. NONE blocks nothing, so an API
hiccup presented the PR as mergeable by a human — an unknown certified
as green, the shape #87 exists to stop, in the one place it never looked.
checks_state now returns UNREADABLE for an absent key versus NONE for a
present-but-empty array, and the sweep leaves an UNREADABLE PR alone
rather than recomputing on facts it did not read. Not a blocker on
purpose: blocking would flap the board on one bad call.
Fixtures 64 -> 66.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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