bug: Vortex::try_from accepts malformed Close packets with payloads

Bug report:

Vortex::try_from(Bytes) accepts Close packets with a non-empty value, even though Close is documented and serialized as a zero-length packet.

Expected behavior:

It should reject malformed Close packets with InvalidLength.

How to reproduce it:

use bytes::{BufMut, Bytes, BytesMut};
use vortex_protocol::{Header, Vortex};
use vortex_protocol::tlv::Tag;

let header = Header::new(Tag::Close, 4);
let header_bytes: Bytes = header.into();
let value = Bytes::from_static(b"test");

let mut packet_bytes = BytesMut::new();
packet_bytes.extend_from_slice(&header_bytes);
packet_bytes.extend_from_slice(&value);

let packet = Vortex::try_from(packet_bytes.freeze());
assert!(packet.is_err());

Current behavior on main: this parses as Vortex::Close(_). If it is serialized again, the payload is dropped.

This is triggerable in practice. The malformed packet is only 10 bytes total, so no cloud quota, API limit, MTU, or resource ceiling gets in the way. Any buggy or malicious peer can send it.

Environment:

• Vortex version: main / 0.1.5
• OS: Linux
• Others: tiny payload, no special setup needed

Start at Vortex::try_from(Bytes) and follow how Header, Tag::Close, and packet payload lengths are validated. Reproduce the malformed Close packet from the issue, then verify that it returns InvalidLength and that valid zero-length Close packets still parse and serialize correctly.