Recovery review prompt names the PR's range, not only the pinned sha

[abedegno]

What

_recovery_review_prompt now tells the out-of-band reviewer that the change under review is the whole pull request as it stands at the pinned commit, naming the range (git diff origin/main...<sha>), not only the head commit's own diff. The self-test asserts the range reaches the prompt text.

Why

On muesli PR #769 (2026-09-18) the recovery review returned PASS after reading one test file. The prompt said "You are reviewing EXACTLY commit ", which exists to pin the tree (#66) but says nothing about how much of it to read. Codex's own Verification section said "Exact commit … reviewed"; the head commit was an 8-line test fix on a 38-file, 4,171-line PR. The run then posted bircher/cross-review=success and the repository's review-gate went green on a PR whose substance no second vendor had read.

On muesli #766 the same words produced a whole-PR review, so this is reviewer interpretation of an ambiguous prompt. The gate cannot distinguish the two readings; only the prompt can.

Evidence

• PR #769's cross-review comment (2026-09-18 18:16 UTC): "The commit only corrects a DB-backed regression test … Exact commit 084bd039… reviewed."
• git diff --stat origin/main...084bd03: 38 files, 4,171 insertions. git show --stat 084bd03: 1 file, 8 insertions.
• Bircher live log: docs/design/front-half-live-log.md, section "#769 recovered: codex PASS on eight lines of a four-thousand-line PR" (branch docs/live-proof-e10, PR docs: live log E10 -- the first attempt, outcome 2 #100).

Verification

• bash -n batch/run-queue.sh passes; the self-test's new assertion fails on the previous prompt text and passes on this one.
• Deployed to the runner from this branch via batch/update-bundle.sh fix/recovery-review-range (which runs the self-test) and exercised by re-running --recover-pr i764 769 codex; the outcome is recorded on muesli PR #769.

[abedegno]

Superseded by the gate-integrity PR, which carries the range sentence in the coordinator's prompt (the only pipeline copy now) and in the cross-review skill's template.