debug: Add debug output for ChaCha20-Poly1305

Found: TAG mismatch between encrypt and decrypt
- Encrypt produces: b3a7f2c8...
- Decrypt expects: f6e6610c...

Root cause: Likely AAD processing difference
Need to compare encrypt/decrypt paths in detail.

WireGuard tests: 28 passed, 4 failed

src/se050_wireguard.c

@@ -23,6 +23,7 @@
 #include <string.h>
 #include <stdint.h>
 #include <stdlib.h>
+#include <stdio.h>
 
 /* =========================================================================
  * WireGuard Protocol Constants
@@ -322,6 +323,8 @@ int se050_wireguard_decrypt_packet(se050_wireguard_session_t *session,
     memzero_explicit(tag, 16);
     
     if (ret < 0) {
+        fprintf(stderr, "DEBUG: decrypt failed, ciphertext_len=%zu, packet_len=%zu, aad_len=16\n", 
+                ciphertext_len, packet_len);
         return -1;
     }