WASM bridge: web client now uses same crypto as CLI (full interop)

warzone-wasm crate:
- Compiles warzone-protocol to WebAssembly via wasm-pack
- Exposes WasmIdentity, WasmSession, decrypt_wire_message to JS
- Same X25519 + ChaCha20-Poly1305 + X3DH + Double Ratchet as CLI
- 344KB WASM binary (optimized with wasm-opt)

WireMessage moved to warzone-protocol:
- Shared type used by CLI client, WASM bridge, and TUI
- Guarantees identical bincode serialization across all clients

Web client rewritten:
- Loads WASM module on startup (/wasm/warzone_wasm.js)
- Identity: WasmIdentity generates same key types as CLI
- Registration: sends bincode PreKeyBundle (same format as CLI)
- Encrypt: WasmSession.encrypt/encrypt_key_exchange
- Decrypt: decrypt_wire_message (handles KeyExchange + Message)
- Sessions persisted in localStorage (base64 ratchet state)
- Groups: per-member WASM encryption (interop with CLI members)

Server routes:
- GET /wasm/warzone_wasm.js — serves WASM JS glue
- GET /wasm/warzone_wasm_bg.wasm — serves WASM binary
- Both embedded at compile time via include_str!/include_bytes!

Web ↔ CLI interop now works:
- Same key exchange (X3DH with X25519)
- Same ratchet (Double Ratchet with ChaCha20-Poly1305)
- Same wire format (bincode WireMessage)
- Web user can message CLI user and vice versa

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

warzone/crates/warzone-protocol/src/message.rs

@@ -33,3 +33,22 @@ pub enum MessageContent {
     File { filename: String, data: Vec<u8> },
     Receipt { message_id: MessageId },
 }
+
+/// Wire message format for transport between clients.
+/// Used by both CLI and WASM — MUST be identical for interop.
+#[derive(Clone, Serialize, Deserialize)]
+pub enum WireMessage {
+    /// First message to a peer: X3DH key exchange + first ratchet message.
+    KeyExchange {
+        sender_fingerprint: String,
+        sender_identity_encryption_key: [u8; 32],
+        ephemeral_public: [u8; 32],
+        used_one_time_pre_key_id: Option<u32>,
+        ratchet_message: crate::ratchet::RatchetMessage,
+    },
+    /// Subsequent messages: ratchet-encrypted.
+    Message {
+        sender_fingerprint: String,
+        ratchet_message: crate::ratchet::RatchetMessage,
+    },
+}