decision: amend ADR-0026 for maintainer-elected fallback reviews

[ss-o]

Problem

ADR-0026 (decision 3) allows the fallback review only after a Copilot request "is not registered", and makes the opening line Fallback review under ADR-0026: Copilot request not registered on <sha> part of that procedure. It does not cover a maintainer choosing the fallback up front to save review allowance.

On 2026-09-26 the maintainer chose exactly that for the commit-lint caller wave: fallback reviews on the ten class 2-4 pull requests, a Copilot request only on the two class 1 ones. No Copilot request was made on the ten, but each review opens with the ADR marker, so the record on these pull requests says a request failed when none was made:

z-shell/F-Sy-H#192, z-shell/z-a-default-ice#12, z-shell/z-a-eval#11, z-shell/z-a-meta-plugins#102, z-shell/zd#125, z-shell/zpmod#114, z-shell/zsh#23, z-shell/zsh-eza#125, z-shell/zsh-fancy-completions#68, z-shell/zunit#27.

Each now carries a correction comment.

A second gap showed up at the same time. Decision 3 treats every unregistered request as "blocked on quota". On z-shell/wiki#926 and z-shell/src#228, POST requested_reviewers with copilot-pull-request-reviewer[bot] returned 201, and no review_requested event followed. Quota exhaustion is one explanation, but an API or reviewer-identifier problem looks identical, and the ADR gives no way to tell them apart.

Proposal

1. Add a maintainer-elected fallback for classes 2-4 with its own marker line, for example Fallback review under ADR-0026: maintainer elected, no Copilot request on <sha>.
2. In decision 3, state how to confirm quota before declaring it: the request path that is known to register, and what the requester's allowance page shows.
3. Say whether the ten reviews above should be amended in place or left with their correction comments.

Relates to #642.

[ss-o]

Evidence from 2026-09-26 on z-shell/zsh-lint, relevant to how the fallback is recorded as well as when it is elected.

• ci(corpus): guard F-Sy-H and the Zsh Completion tree against regressions (#470) zsh-lint#486, docs(branching): define Dependabot security-update exception for main guards #487, fix: use METRICS_TOKEN for cross-org repository template steps in metrics workflow #489 and fix(ci): stop profile deploys overwriting wiki #491 each merged under a review opening with Fallback review under ADR-0026: Copilot request not registered on <sha>, after a real Copilot request that returned an empty reviewer list. The marker was accurate.
• None of the four was executed under .github/skills/code-review/SKILL.md against code-review-generic.instructions.md, as ADR-0026 decision 3 requires. Each was the agent's summary of its own verification, with no inline threads. The skill was never loaded in that session.
• On fix: use METRICS_TOKEN for cross-org repository template steps in metrics workflow #489 the review was submitted on 6789946 at 16:39:42Z. The branch was force-pushed (a rebase) at 16:40:07Z, and the pull request was squash-merged on e0d04ce at 16:42:32Z without a new review. --match-head-commit guarded the merge against a race, not against a stale review.

If the amendment here touches the procedure, two points would close these gaps: the marker line should be accompanied by evidence that the checklist ran (for example the checklist items with a verdict each), and any push after the fallback review voids it.

[ss-o]

Maintainer decision (ss-o, 2026-09-26): allow the fallback to be elected up front, with a distinct marker.

• Scope: classes 2-4, as for the existing fallback. Class 1 still waits for Copilot or a second human.
• Marker: a maintainer-elected fallback review opens with Fallback review under ADR-0026: maintainer elected, no Copilot request on <sha>. The existing Copilot request not registered on <sha> marker stays for the case where a request was made and did not register.
• Content is the same in both cases: the review is executed under .github/skills/code-review/SKILL.md against code-review-generic.instructions.md on the current head and posted with inline threads. A marker line alone is not a review.
• Any push after the review, a rebase included, voids it; a new fallback is posted on the new head.

This will be written into the ADR-0026 amendment and into the pull-request runbook proposed under #668.

[ss-o]

Maintainer decision (ss-o, 2026-09-26): the review of record where Copilot code review is not configured.

• Where a repository, or the base branch of a pull request, has no Copilot code review configured, the review of record is a human review or, in classes 2 to 4, a maintainer-elected fallback under this issue's marker Fallback review under ADR-0026: maintainer elected, no Copilot request on <sha>.
• Examples today: z-shell/F-Sy-H main and z-shell/zi next have no copilot_code_review rule.
• Class 1 is unchanged: it waits for Copilot or a second human.

This goes into the ADR-0026 amendment together with the up-front election decided above, and into the AGENTS.md done gate, which today speaks only of "every configured review". The pull-request runbook in #670 cites it as an interim rule until then.

[ss-o]

Resolved by PR #677 (commit eee964a). ADR-0026, AGENTS.md, and runbooks/pull-requests.md codified the maintainer-elected fallback review for classes 2-4 under marker Fallback review under ADR-0026: maintainer elected, no Copilot request on .