fix: set non-zero exit code when teardown throws during close

[zakcutner]

Description

Errors thrown while closing Vitest, most notably a failing globalSetup teardown, were logged but never affected the exit code. As a result vitest run exited 0 even though cleanup failed.

vitest.close() catches teardown errors since #9573, so that the rest of the shutdown still runs, and logs them via logger.error('error during close', ...). However, nothing set a non-zero exit code afterwards, so any cleanup failure in a globalSetup teardown was silently swallowed.

This change routes the collected errors, meaning teardown errors plus any rejected close promises, through the existing _checkUnhandledErrors. That is the same mechanism used for unhandled test errors. It sets process.exitCode to 1 and honours dangerouslyIgnoreUnhandledErrors.

Reproduction

A globalSetup whose teardown throws, with otherwise passing tests:

// globalSetup.ts
export default function () {
  return () => {
    throw new Error('teardown error')
  }
}

Before this change, vitest run prints the error but exits 0. After, it exits 1.

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[AriPerkkio]

Reporting project._teardownGlobalSetup() errors as unhandled errors makes sense to me. I'm not fully sure if pool closing and project cleanups should be treated too. Though why not 🤔