fix(ext/node): reject postMessage of FileHandle without transfer
Mark FileHandle.prototype as non-serializable so passing a
FileHandle to MessagePort.postMessage / structuredClone produces
DataCloneError instead of silently round-tripping as `{}`. The
check is skipped when the value is itself in the transfer list,
matching Node's semantics.
Picks up the first assertion of
test-worker-message-port-transfer-filehandle; the remaining
assertions require a JSTransferable mechanism that's not in
scope here.
