Self-test: add X3DH shared secret comparison for debugging

Shows alice_shared vs bob_shared to verify X3DH produces same secret.

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

warzone/crates/warzone-wasm/src/lib.rs

@@ -257,10 +257,23 @@ pub fn self_test() -> Result<String, JsValue> {
 
     let text = result.get("text").and_then(|v| v.as_str()).unwrap_or("MISSING");
 
+    // More detailed info
+    let alice_shared_hex = hex::encode(x3dh_result.shared_secret);
+
+    // Bob's side: compute shared secret for comparison
+    let bob_shared = x3dh::respond(
+        &bob_id, &bob_spk_secret, None,
+        &alice_pub.encryption, &x3dh_result.ephemeral_public,
+    ).map_err(|e| JsValue::from_str(&format!("X3DH respond direct: {}", e)))?;
+    let bob_shared_hex = hex::encode(bob_shared);
+
+    let shared_match = alice_shared_hex == bob_shared_hex;
+
     Ok(format!(
-        "WASM self-test: alice_fp={}, bob_fp={}, wire_bytes={}, decrypted='{}', PASS={}",
+        "alice_fp={}, bob_fp={}, wire_bytes={}, alice_shared={}..., bob_shared={}..., shared_match={}, decrypted='{}', PASS={}",
-        alice_pub.fingerprint, bob_pub.fingerprint, wire_bytes.len(), text,
+        alice_pub.fingerprint, bob_pub.fingerprint, wire_bytes.len(),
-        text == "hello from WASM self-test"
+        &alice_shared_hex[..16], &bob_shared_hex[..16], shared_match,
+        text, text == "hello from WASM self-test"
     ))
 }