fix(test): enforce the Node version pin on every test run, not just install

[JSONbored]

Context

#7613 added engine-strict=true to a root .npmrc, so npm install/npm ci now hard-fails on a Node
version outside engines.node. That closes the most common trigger (fresh clone, pulling main,
switching branches, CI-style setup) -- confirmed directly: npm install on Node 26 now fails with
EBADENGINE.

It does not close every path, though: engine-strict fires during npm's dependency-resolution step, not
on every subsequent npm run. If node_modules is already installed (built while on the pinned Node)
and someone simply switches their shell's active node afterward -- nvm use 26, a homebrew default
changing, etc. -- with no reinstall, every later npm run sails straight past engine-strict silently.
Confirmed directly: npm run engines-nvmrc:check succeeded on Node 26 despite engine-strict=true and a
tightened engines.node, because it never re-triggers npm's install-time check. That's uncomfortably
close to the actual mechanism that let the Node 26 jsdom/localStorage bug (#7592/#7597, #7612) go
unnoticed twice: confusing downstream test failures instead of one clear "wrong Node version" message.

Requirements

• Add a small scripts/check-node-version.mjs that checks process.version against root
  package.json's engines.node and fails with a clear, actionable message (not npm's more cryptic
  EBADENGINE format) when they don't match.
• Wire it as a pretest* hook (npm's standard pre-script convention) on the commands that actually run
  vitest: test, test:ci, test:coverage, test:workers, ui:test -- so each fires the check
  immediately, before doing any real work, regardless of node_modules' install state.

Deliverables

• scripts/check-node-version.mjs (+ .d.mts + unit tests).
• pretest, pretest:ci, pretest:coverage, pretest:workers, preui:test wired in package.json.
• Verified directly on Node 26: npm test, npm run test:ci, and npm run ui:test each fail
  immediately with the clear message, without running any real work first.
• npm run test:ci green on Node 22 (no regression for the compliant case).

Test Coverage Requirements

scripts/** and test/** are outside Codecov's src/**-only include glob, so this owes no
patch-coverage number -- but the new script ships its own unit suite (satisfying/failing/no-engines-field
cases, a real-repo-state regression guard, and a subprocess smoke test for the passing case), matching
this repo's existing check-script test convention.

Expected Outcome

Running any of the guarded commands on a Node version outside .nvmrc's pin fails immediately and
clearly, whether or not node_modules was already installed under a different Node.

Links & Resources

• chore(deps): enforce the .nvmrc Node 22 pin locally (engine-strict + engines.node upper bound) #7613 -- the engine-strict/engines.node work this closes the remaining gap in
• fix(test): Node 26 jsdom localStorage gap in apps/loopover-ui and packages/loopover-ui-kit #7612 -- the Node 26 jsdom/localStorage bug this whole line of work exists to stop recurring

[linear-code]

JSO-5388