spec: ci-test-shards

[yihanzhu]

Tracks #269

G2 spec for the merged intent (G1, PR #270). Frontmatter records intent-blob e56b92429ca56a638827ebf7d0e270ffa2bd1089 and risk: high (the change edits .github/workflows/ci.yml, the merge gate's workflow and a constitution path). Merging this PR accepts both. It does not close the intake issue.

This PR adds only work/ci-test-shards/spec.md.

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[yihanzhu]

Codex reviewer (cross-vendor, read-only)

Reviewed-head: 45a92ef
Reviewed-base: 4965175
reviewer: gpt-5.5 @ high

Posted verbatim by codex-review.sh (codex exec review --json --base refs/codex-review/274-98076/base in an isolated temp worktree, sandbox forced read-only). Comments only — Codex never pushes, approves, or merges.

The new spec is hash-linked to the accepted intent, records high risk, and stays within the artifact path. I did not find a discrete blocking issue in the proposed requirements or process.

[yihanzhu]

Codex reviewer (cross-vendor, read-only)

Reviewed-head: 1ba4bde
Reviewed-base: 40582c2
reviewer: gpt-5.5 @ high

Posted verbatim by codex-review.sh (codex exec review --json --base refs/codex-review/274-6458/base in an isolated temp worktree, sandbox forced read-only). Comments only — Codex never pushes, approves, or merges.

The added spec contains an impossible acceptance condition because it also requires adding a new discovered test suite. That contradiction should be fixed before the spec is accepted as the implementation contract.

Review comment:

• [P2] Remove the impossible output-diff requirement — /private/var/folders/rm/bkx4f4b91vqfn79vk02pcd140000gn/T/tmp.ncmVsKLDHp/work/ci-test-shards/spec.md:27-30
  This verification cannot pass once requirement 9 is implemented: the new executable scripts/test/run-all-sharding.test.sh will be discovered by the unchanged find ... '*.test.sh' rule and run in no-argument mode, so the output and final count will gain at least that suite instead of diffing exactly against today's output. The spec should require preserving the existing suites' behavior/order, or explicitly account for the new focused test.

[yihanzhu]

Codex reviewer (cross-vendor, read-only)

Reviewed-head: 731f7c5
Reviewed-base: 40582c2
reviewer: gpt-5.5 @ high

Posted verbatim by codex-review.sh (codex exec review --json --base refs/codex-review/274-14100/base in an isolated temp worktree, sandbox forced read-only). Comments only — Codex never pushes, approves, or merges.

The spec contains a scope contradiction that would make the required sharding regression test appear out-of-scope during implementation. This should be clarified before accepting the artifact.

Review comment:

• [P2] Align the out-of-scope list with the required test — /private/var/folders/rm/bkx4f4b91vqfn79vk02pcd140000gn/T/tmp.L4OCwc4vff/work/ci-test-shards/spec.md:175-176
  When this spec becomes the accepted G2 scope, requirement 9 requires adding scripts/test/run-all-sharding.test.sh, but this out-of-scope bullet forbids any change to which suites exist or which CI runs. Because this repo treats spec.md as the hash-linked artifact required before planning (work/README.md:26-29), the implementation is both required and out-of-scope; clarify this to mean no change to existing suites, or explicitly exempt the focused sharding test.

[yihanzhu]

Codex reviewer (cross-vendor, read-only)

Reviewed-head: 7ec0664
Reviewed-base: 40582c2
reviewer: gpt-5.5 @ high

Posted verbatim by codex-review.sh (codex exec review --json --base refs/codex-review/274-39156/base in an isolated temp worktree, sandbox forced read-only). Comments only — Codex never pushes, approves, or merges.

The spec otherwise follows the high-risk artifact shape, but it adds a discovered test suite despite the accepted intent explicitly keeping the suite set and no-argument runner behavior unchanged.

Review comment:

• [P2] Keep the no-argument suite set in scope — /var/folders/rm/bkx4f4b91vqfn79vk02pcd140000gn/T/tmp.WpmSJWWMEU/work/ci-test-shards/spec.md:34-35
  Under the artifact chain, the spec is the next hash-linked artifact after the accepted intent (AGENTS.md:370-379), and that intent says “No change to which suites exist” and keeps the no-argument runner unchanged (work/ci-test-shards/intent.md:33-37). Requiring a new discovered *.test.sh suite widens that accepted scope and intentionally changes no-selector output; either re-accept the intent for the added suite or keep the sharding check outside the discovered suite set.