Clean up TypeScript test validators and run regression tests in CI #463

Summary

Address two pre-existing TypeScript test-infrastructure gaps surfaced while reviewing #461:

1. Test-created validators are not closed, allowing native compiler processes to accumulate during a test run.
2. The Node.js CI workflow builds the project but does not execute npm test.

This issue tracks both improvements separately from the standard-library helper changes in #461. It is not a report of a correctness regression in those declarations.

Validator lifecycle

The shared test helper creates a validator for each test without registering teardown. With TypeScript 7, each validator owns a native compiler process; calling close() releases it.

Observed behavior

Validation at commit 5547207293c9f787b6fc3f3a6f729d9d977bd472 on Windows, Node.js 24.19.0, and TypeScript 7.0.2:

• Library and test compilation succeeded.
• The unmodified validator suite finished with 8 passing and 17 failing tests. Failures included out of memory allocating heap arena map, Error: spawn UNKNOWN, and SyncRpcChannel: timed out connecting to named pipe.
• Re-running the same suite with temporary per-test teardown that closed each created validator produced 25 passing tests and 0 failures, without changing the validator implementation or test assertions.

The resource failures are environment-dependent. The fixture pattern predates #461, but that PR adds another 13 validator instances, making explicit cleanup increasingly important.

Reproduction

From the TypeScript package directory at the reviewed commit, using PowerShell:

npm ci --ignore-scripts
npm run build
npx --no-install tsc -p test
node --test --test-reporter=spec .\out\validate.test.js

Compare with a run that registers cleanup for each validator through test teardown, such as t.after(() => validator.close()). Cleanup must also run when an assertion fails.

CI coverage

The Node.js CI workflow runs npm ci and npm run build-all, but does not run npm test. Consequently, the existing regression suite and the new tests in #461 are not automatically enforced by this workflow.

At the time of review, the referenced Node.js CI run reported action_required. That status, and the successful CLA check on the PR, are not evidence of successful build or test execution. The missing test step remains a separate workflow gap.

Requested changes

• Ensure test-created TypeScript validators are closed during test teardown, preferably through the shared fixture so existing and new tests benefit.
• Add npm test to the Node.js CI workflow for each supported Node version, retaining the existing library/example build coverage.
• Keep the regression tests runnable offline without live model services or credentials.

Acceptance criteria

• Test-created validators are explicitly closed, including when assertions fail, rather than retaining all compiler processes until the test process exits.
• The focused validator suite passes without temporary cleanup instrumentation.
• npm test and npm run build-all pass across the workflow's supported Node.js matrix.
• CI logs show actual regression-test execution, and a failing test fails the job.

Related: #461, #452.