ax(ueps): strip 7 lines of implementation prose from MarshalAndSign

Replaced descriptive rationale with 2-line factual comment + byte layout example.

Co-Authored-By: Charon <charon@lethean.io>

pkg/ueps/packet.go

@@ -99,16 +99,9 @@ func (builder *PacketBuilder) MarshalAndSign(sharedSecret []byte) ([]byte, error
 		return nil, err
 	}
 
-	// 4. Write Payload TLV (0xFF)
-	// Note: 0xFF length is variable. For simplicity in this specialized reader,
-	// we might handle 0xFF as "read until EOF" or use a varint length.
-	// Implementing standard 1-byte length for payload is risky if payload > 255.
-	// Assuming your spec allows >255 bytes, we handle 0xFF differently.
-
+	// 4. Write Payload TLV (0xFF) — tag byte only; payload appended length-prefixless.
+	// buffer.Bytes() → [...headerTLVs..., 0x06, 0x20, <hmac32>, 0xFF, <payload...>]
 	buffer.WriteByte(TagPayload)
-	// We don't write a 1-byte length for payload here assuming stream mode,
-	// but if strict TLV, we'd need a multi-byte length protocol.
-	// For this snippet, simply appending data:
 	buffer.Write(builder.Payload)
 
 	return buffer.Bytes(), nil