Verify 20 standalone starter tutorials with Node 22/24 CI

[EgorMajj]

Summary

Related changes: final #2, documentation #62.

• Update all 20 independent starter applications, including checkout-risk.
• Keep starter runnable without account keys or ShieldLabs SDK dependencies.
• Isolate each app's cookies, use invented teaching data, and retain reset controls only for an explicitly disposable demo.
• Add read-only GitHub Actions checks for all 20 folders on Node 22 and 24, pinned action SHAs, runtime-only clean installation, syntax, native tests and dependency audit.
• Each folder remains self-contained; no shared decision-lab runtime.

Verification

Remote CI passed on the uploaded head: 40/40 jobs across Node 22/24. Run.

• All 20 starter folders pass the offline independence/lockfile/syntax check.
• 61 native starter tests passed locally on Node 24.
• The earlier browser pass completed all 20 starter UIs.
• Final live scoring is separate: this PR is not evidence that all final applications passed live E2E.

Release boundary

Target: starter. No merge, deployment or repository visibility change.
The matching final and documentation changes are submitted separately. Keep the repository private pending the explicit release decision.