AES-256-CBC doesn't guarantee throwing on wrong key decryption - it depends
on whether the decrypted bytes happen to have valid PKCS#7 padding. The test
now verifies that decryption either throws OR returns a value different from
the original plaintext.
This fixes flaky test failures that started appearing after the Vitest 4.0
upgrade, where the 'Closing rpc while fetch was pending' error was a secondary
symptom of the test failure causing worker teardown during module loading.
Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
