chore(armory): engines.node drift-prevention gate — closes queue #31

[Goosterhof]

Summary

Closes war-room enforcement queue #31 — adds a CI-time presence gate so any future workspace package (or the root manifest) that ships without an engines.node declaration fails Gate 6 of the 8-gate pipeline. The declarations themselves landed 2026-04-22 in commit 0605d99 (root + all 10 packages declare engines.node: ">=24.0.0"); without this guard, the next package added to the Armory (fs-auth, fs-validation, future) can ship without the declaration and consumers get silent Node-version mismatches instead of EBADENGINE.

Shape — Option α (fold into scripts/lint-pkg.mjs)

Picked α over a new scripts/check-engines.mjs + 9th CI gate because the engines.node presence check sits in exactly the same domain as the existing publint suggestion-strictness wrapper (queue #33, PR #35 follow-up): both are per-manifest publish-readiness assertions over the same packages/* corpus, both share the same failures[] collection shape, and both already iterate the same loop. Folding keeps the CI gate count at 8 and the script discovery surface small.

Filename scripts/lint-pkg.mjs retained deliberately — renaming to scripts/check-packages.mjs (more accurate now that it covers two assertion classes) would force a parallel edit to the lint:pkg npm-script alias and the .github/workflows/ci.yml npm run lint:pkg step, neither of which is in scope for this PR. The expanded responsibility is documented in the script's header comment.

What this gate asserts

For every package.json in packages/*/ and the workspace root package.json:

1. If the file is missing engines entirely → fail.
2. If engines.node is missing or not a non-empty string → fail.

The gate is presence, not value. It does NOT enforce >=24.0.0 specifically — value alignment is a separate doctrine question tracked alongside the CI workflow's node-version. If a future bump moves the corpus to >=26.0.0, the gate does not need editing.

Smoke test — gate fires correctly

Per orders §F:

1. Temporarily deleted the engines block from packages/storage/package.json.
2. Ran npm run lint:pkg.
3. Result: exit code 1, named failure surfaced:

   @script-development/fs-storage: engines field missing (queue #31 — engines.node presence required)
   
   lint:pkg gate FAILED (1):
     - @script-development/fs-storage: engines field missing (queue #31 — engines.node presence required)
   

4. Reverted the deletion.
5. Re-ran npm run lint:pkg.
6. Result: exit code 0:

   lint:pkg gate PASS — 10 packages + root clean (engines.node present; publint suggestions/warnings/errors all treated as fatal).
   

Full local CI matrix — all 8 gates green

Gate	Status	Notes
1. npm audit	PASS (exit 0)	1 high dev-dep advisory (fast-uri) pre-exists on main — not introduced by this PR
2. format:check	PASS	532 files, oxfmt clean
3. lint	PASS	0/0 warnings/errors, 332 files
4. build	PASS	10 packages, tsdown clean
5. typecheck	PASS	10 packages, tsc --noEmit clean
6. lint:pkg	PASS	10 packages + root clean, engines.node assertion fires on intentional omission
7. test:coverage	PASS	Per-package 100% thresholds met
8. test:mutation	PASS	Final 93.33% ≥ 90% threshold

Files changed

• scripts/lint-pkg.mjs (+53 / -11) — checkEnginesNode() helper, root-manifest check before the per-package loop, header comment updated to reference queue Fix setById reactivity by invalidating adapted cache #31 alongside queue fs-packages M1 moderate remediation (Armorer) #33.
• CLAUDE.md (+2 / -2) — one-sentence note appended to the Stack §Package lint bullet (doctrine-propagation per war-room CLAUDE.md).

Reviewer checklist

• Diff scripts/lint-pkg.mjs to confirm the assertion is presence-only (no value validation).
• Confirm the failure message format names the offending package (one-grep diagnosis).
• Confirm CLAUDE.md update matches the implementation (queue Fix setById reactivity by invalidating adapted cache #31 + 2026-05-12 + commit 0605d99 reference).
• Smoke-test result above is the proof point — feel free to reproduce locally.

References

• Enforcement queue Fix setById reactivity by invalidating adapted cache #31 (war-room enforcement/queue.md)
• Deployment order: orders/fs-packages/queue-31-engines-node-drift-prevention-gate-armorer-deployment.md
• Prior Armorer deployment that landed declarations: commit 0605d99, 2026-04-22
• Sibling pattern: queue fs-packages M1 moderate remediation (Armorer) #33 publint suggestion-strictness wrapper (same script, same domain)

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