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Why:
- The root Node 20.9 contract predates direct runtime dependencies whose declared minimums now reach Node 22.19.
- README, contributor, localized docs, and the OpenMAIC extension skill repeated the stale supported-version claim.

What:
- Raise the root Node minimum to 22.19 and align every operator, contributor, locale, and skill prerequisite.
- Add a check that compares the root minimum with installed direct production dependency engine minimums.
- Run the new contract check in CI after the frozen dependency install.

Risk:
- This changes the declared minimum only; no upper bound is added and Node 24 compatibility remains a separate concern.
- The localized docs build was validated with the independent #1306 boundary fix from PR #1307, which is not included here.

Tests:
- RED on the base: engine check reported pi-agent-core, pi-ai, svg-pathdata, and undici floors
- GREEN: root minimum 22.19 satisfies 35 engine-constrained direct dependencies
- Node 20 lockfile-only install reports the root unsupported-engine warning
- Node 22 frozen install and postinstall
- Docs build with PR #1307 boundary: 34 pages and all locale postexport checks; docs types:check
- Root Prettier, ESLint, TypeScript, i18n, package-version, and internal-dependency gates
- Root pnpm test: 7137 passed, 81 skipped

Live Docs:
- GitHub issue #1304 tracks the Node contract; #1306 / PR #1307 tracks the separate docs-build prerequisite.
Co-authored-by: wyuc <wang-yc24@mails.tsinghua.edu.cn>