Fix spurious "short buffer" warnings during message decode (#1223)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kixelated

rs/moq-lite/src/ietf/message.rs

@@ -52,6 +52,9 @@ impl<T: Message> Decode<Version> for T {
 				}
 			}
 		} else {
+			if buf.remaining() < size {
+				return Err(DecodeError::Short);
+			}
 			let mut limited = buf.take(size);
 			match Self::decode_msg(&mut limited, version) {
 				Ok(result) => {

rs/moq-lite/src/lite/message.rs

@@ -49,6 +49,9 @@ impl<T: Message> Decode<Version> for T {
 				}
 			}
 		} else {
+			if buf.remaining() < size {
+				return Err(DecodeError::Short);
+			}
 			let mut limited = buf.take(size);
 			match Self::decode_msg(&mut limited, version) {
 				Ok(result) => {