feat: multi-wallet architecture with localStorage state, EIP-712 verification, cross-tab WS leadership

- wallets.js: WalletManager state management with chain validation
- verifier.js: WalletVerifier EIP-712 signing via window.ethereum
- stream.js: WalletStreamManager with BroadcastChannel leader election, backoff + jitter
- AGENTS.md: updated with coding guidelines

package.json

@@ -0,0 +1,5 @@
+{
+  "name": "dione",
+  "type": "module",
+  "private": true
+}