091-an-unclassified-review-failure-blocks-the-merge

An unclassified review failure blocks the merge

The AI review job classifies a failed reviewer invocation into two outcomes, and its fall-through is a pass. On 2026-09-20 the provider returned "Your organization does not have access to Claude. Please login again or contact your administrator." and the job matched it against a token allowlist (`authentication_error`, `permission_error`, `unauthorized`, `forbidden`, and three more), found no match, set `review_status=api_failure`, exited 0, and `ci-gate` went green on PR #267 with no review. The refusal was prose and the allowlist reads tokens, so an access refusal took the transient-outage branch. Two further holes sit beside it: `review_status=ok` is set from exit status alone, so a reviewer that exits 0 having written nothing publishes an empty review the gate reads as reviewed, and the transient notice swallows a failed `gh pr comment` with a warning, so the one artifact that makes a skip visible can be absent while the gate still passes. This spec states the classification policy the job must implement: success and failure are separated by exit status before any text is read, refusal signals outrank transient signals inside a failed invocation, transient signals are recognized only in the contextual forms their emitting layer produces, and everything else blocks. It is defended by a test that executes the workflow's own script rather than a copy of its patterns, so inverting a blocking branch is caught even when its regexes are untouched.