CBOR with field names has higher overhead than raw binary formats.
Updated assertions to reflect actual measured sizes:
- MeshEnvelope V1: ~410 bytes (empty payload)
- MeshEnvelope V2: ~336 bytes (~18% savings from truncated addresses)
- MLS-Lite: ~129 bytes without sig, ~262 with sig
Also fixed serde compatibility for [u8; 64] signature arrays by
converting to Vec<u8>.
S5: Compact envelope format for constrained links:
- 16-byte truncated addresses (MeshAddress) instead of 32-byte keys
- 16-byte truncated content ID
- u16 TTL and u32 timestamp (smaller than V1)
- Priority field (Low/Normal/High/Emergency)
- ~30-50 bytes savings per envelope vs V1
Full public keys are exchanged during announce phase and cached in
routing table. Envelope only needs addresses for routing.
