`vaptvupt info` mislabelled full post-quantum (--pq-only, enc_type 0x06)
archives as "PQ Hybrid: YES (ML-KEM-768 + X25519)". Full-PQ archives set
the generic ZUPT_FLAG_PQ_HYBRID header flag (the enc_type byte is what
distinguishes hybrid 0x02 from pure 0x06), but info only checked the flag.
info now seeks to hdr.encryption_header_off, reads the real enc_type from
the encryption-header block, and reports the actual mode: "ML-KEM-768
only, no classical layer" for --pq-only, and hybrid / SDK-v2 / sealed-box
for the others. Reader-side only — no wire-format change; existing 4.2.0
archives are relabelled correctly with no re-encryption.