Batch-merged with the owner's 2026-10-10 hold/backlog PR wave (/merge-batch). Validated in one combined tree of 43 boarded PRs on top of release/v3.8.52 (048d9e2f): typecheck:core, check:open-sse-typecheck, check-deps, check-test-discovery, changelog-integrity, complexity + cognitive ratchets, check:docs-all, i18n UI coverage, ESLint on the 142 changed source files - green; 58 changed node:test files 584/586 (2 timing flakes in video-retention-http-12150 that pass in isolation) and 3 vitest files 116/116. File-size overruns in that tree belong only to PRs held out of this wave (#16110, #16112, #16140, #15790). Warning: base-red inherited: #15306.