feat: Server auto-sense falls back to DTLS 1.2 f a DTLS 1.3 ServerHello is fragmented #88
Description
Firefox 148+ sends X25519MLKEM768 as its primary key_share, making the ClientHello too large for a single DTLS record. The supported_versions extension ends up in a later fragment, causing the auto-sense server to miss it and fall back to DTLS 1.2.