feat: WarzonePhone lossy VoIP protocol — Phase 1 complete

Rust workspace with 7 crates implementing a custom VoIP protocol
designed for extremely lossy connections (5-70% loss, 100-500kbps,
300-800ms RTT). 89 tests passing across all crates.

Crates:
- wzp-proto: Wire format, traits, adaptive quality controller, jitter buffer, session FSM
- wzp-codec: Opus encoder/decoder (audiopus), Codec2 stubs, adaptive switching, resampling
- wzp-fec: RaptorQ fountain codes, interleaving, block management (proven 30-70% loss recovery)
- wzp-crypto: X25519+ChaCha20-Poly1305, Warzone identity compatible, anti-replay, rekeying
- wzp-transport: QUIC via quinn with DATAGRAM frames, path monitoring, signaling streams
- wzp-relay: Integration stub (Phase 2)
- wzp-client: Integration stub (Phase 2)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-crypto/src/lib.rs

@@ -0,0 +1,23 @@
+//! WarzonePhone Crypto Layer
+//!
+//! Implements the cryptographic primitives compatible with the Warzone messenger identity model:
+//! - Identity: 32-byte seed -> HKDF -> Ed25519 (signing) + X25519 (encryption)
+//! - Fingerprint: SHA-256(Ed25519 pub)[:16]
+//! - Per-call: Ephemeral X25519 key exchange -> ChaCha20-Poly1305 session
+//! - Nonce: Derived from session_id + seq + direction (not transmitted)
+//! - Rekeying: Periodic ephemeral exchange with HKDF mixing for forward secrecy
+
+pub mod anti_replay;
+pub mod handshake;
+pub mod nonce;
+pub mod rekey;
+pub mod session;
+
+pub use anti_replay::AntiReplayWindow;
+pub use handshake::WarzoneKeyExchange;
+pub use nonce::{build_nonce, Direction};
+pub use rekey::RekeyManager;
+pub use session::ChaChaSession;
+
+// Re-export trait types from wzp-proto for convenience.
+pub use wzp_proto::{CryptoError, CryptoSession, KeyExchange};