Use the same AES factory for a closed AesManaged local

Replace parameterless AesManaged plain-local construction with Aes.Create(), preserving its existing lifetime. Require every reference to be an attributed forwarded property or transform/key-generation receiver. Retype the local and members consistently. Exclude using resources, initialization, escapes, captures, identity, explicit disposal, async/iterators, directives and conditional snapshots. Opt-in modern-.NET compatibility; no mode/key/format choice.