feat(multisig): implement EVM Safe, BTC P2WSH, and Solana adapters

EVM Safe adapter: Deploy Safe with 3 owners/threshold 2, EIP-712 signing,
supports ETH, Polygon, Base, Arbitrum, Optimism, BSC, Avalanche C.

BTC multisig adapter: 2-of-3 P2WSH with BIP-67 pubkey sorting,
PSBT-based transaction building for BTC, LTC, DOGE.

Solana multisig adapter: Squads-style PDA multisig with vault,
proposal-based transaction execution for SOL.

All adapters include comprehensive tests with mocked chain interactions.

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

Author: ralyodio

src/lib/multisig/adapters/btc-multisig.test.ts

@@ -0,0 +1,189 @@
+/**
+ * BTC Multisig Adapter Tests
+ *
+ * Tests the Bitcoin P2WSH multisig adapter.
+ */
+
+import { describe, it, expect, beforeEach } from 'vitest';
+import { BtcMultisigAdapter } from './btc-multisig';
+
+// Sample compressed public keys (33 bytes hex)
+const PUB_KEY_1 = '02' + '11'.repeat(32);
+const PUB_KEY_2 = '03' + '22'.repeat(32);
+const PUB_KEY_3 = '02' + '33'.repeat(32);
+
+describe('BtcMultisigAdapter', () => {
+  let adapter: BtcMultisigAdapter;
+
+  beforeEach(() => {
+    adapter = new BtcMultisigAdapter();
+  });
+
+  describe('supportedChains', () => {
+    it('should support BTC, LTC, and DOGE', () => {
+      expect(adapter.supportedChains).toContain('BTC');
+      expect(adapter.supportedChains).toContain('LTC');
+      expect(adapter.supportedChains).toContain('DOGE');
+      expect(adapter.supportedChains).toHaveLength(3);
+    });
+  });
+
+  describe('createMultisig', () => {
+    it('should create a P2WSH 2-of-3 multisig address for BTC', async () => {
+      const result = await adapter.createMultisig('BTC', {
+        depositor_pubkey: PUB_KEY_1,
+        beneficiary_pubkey: PUB_KEY_2,
+        arbiter_pubkey: PUB_KEY_3,
+      }, 2);
+
+      expect(result.escrow_address).toBeTruthy();
+      expect(result.escrow_address.startsWith('bc1')).toBe(true);
+      expect(result.chain_metadata.address_type).toBe('P2WSH');
+      expect(result.chain_metadata.witness_script).toBeTruthy();
+      expect(result.chain_metadata.threshold).toBe(2);
+      expect(result.chain_metadata.pubkeys).toHaveLength(3);
+    });
+
+    it('should create deterministic addresses from same pubkeys', async () => {
+      const participants = {
+        depositor_pubkey: PUB_KEY_1,
+        beneficiary_pubkey: PUB_KEY_2,
+        arbiter_pubkey: PUB_KEY_3,
+      };
+
+      const result1 = await adapter.createMultisig('BTC', participants, 2);
+      const result2 = await adapter.createMultisig('BTC', participants, 2);
+
+      expect(result1.escrow_address).toBe(result2.escrow_address);
+    });
+
+    it('should sort pubkeys (BIP-67) for deterministic addresses', async () => {
+      // Same pubkeys, different order — should produce same address
+      const result1 = await adapter.createMultisig('BTC', {
+        depositor_pubkey: PUB_KEY_1,
+        beneficiary_pubkey: PUB_KEY_2,
+        arbiter_pubkey: PUB_KEY_3,
+      }, 2);
+
+      const result2 = await adapter.createMultisig('BTC', {
+        depositor_pubkey: PUB_KEY_3,
+        beneficiary_pubkey: PUB_KEY_1,
+        arbiter_pubkey: PUB_KEY_2,
+      }, 2);
+
+      expect(result1.escrow_address).toBe(result2.escrow_address);
+    });
+
+    it('should reject non-UTXO chains', async () => {
+      await expect(
+        adapter.createMultisig('ETH' as any, {
+          depositor_pubkey: PUB_KEY_1,
+          beneficiary_pubkey: PUB_KEY_2,
+          arbiter_pubkey: PUB_KEY_3,
+        }, 2),
+      ).rejects.toThrow('not supported');
+    });
+
+    it('should reject invalid public key length', async () => {
+      await expect(
+        adapter.createMultisig('BTC', {
+          depositor_pubkey: 'abcdef', // too short
+          beneficiary_pubkey: PUB_KEY_2,
+          arbiter_pubkey: PUB_KEY_3,
+        }, 2),
+      ).rejects.toThrow('Invalid public key length');
+    });
+
+    it('should store witness script in chain_metadata', async () => {
+      const result = await adapter.createMultisig('BTC', {
+        depositor_pubkey: PUB_KEY_1,
+        beneficiary_pubkey: PUB_KEY_2,
+        arbiter_pubkey: PUB_KEY_3,
+      }, 2);
+
+      expect(result.chain_metadata.witness_script).toBeTruthy();
+      expect(typeof result.chain_metadata.witness_script).toBe('string');
+      // Witness script should be hex-encoded
+      expect(/^[0-9a-f]+$/.test(result.chain_metadata.witness_script as string)).toBe(true);
+    });
+  });
+
+  describe('proposeTransaction', () => {
+    it('should build PSBT data for BTC', async () => {
+      const result = await adapter.proposeTransaction('BTC', {
+        escrow_address: 'bc1qmultisig123456789',
+        to_address: 'bc1qbeneficiary123456',
+        amount: 0.5,
+        chain_metadata: {
+          witness_script: 'abcdef0123456789',
+        },
+      });
+
+      expect(result.tx_hash_to_sign).toBeTruthy();
+      expect(result.tx_data.amount_sats).toBe(50000000);
+      expect(result.tx_data.to_address).toBe('bc1qbeneficiary123456');
+    });
+
+    it('should fail without witness_script', async () => {
+      await expect(
+        adapter.proposeTransaction('BTC', {
+          escrow_address: 'bc1qmultisig123456789',
+          to_address: 'bc1qbeneficiary123456',
+          amount: 0.5,
+          chain_metadata: {},
+        }),
+      ).rejects.toThrow('Missing witness_script');
+    });
+  });
+
+  describe('verifySignature', () => {
+    it('should validate signature format', async () => {
+      // 64-byte signature (128 hex chars)
+      const validSig = 'aa'.repeat(64);
+      const valid = await adapter.verifySignature(
+        'BTC',
+        { witness_script: 'abcdef', pubkeys: [PUB_KEY_1] },
+        validSig,
+        PUB_KEY_1,
+      );
+      expect(valid).toBe(true);
+    });
+
+    it('should reject unknown pubkey', async () => {
+      const validSig = 'aa'.repeat(64);
+      const valid = await adapter.verifySignature(
+        'BTC',
+        { witness_script: 'abcdef', pubkeys: [PUB_KEY_2] },
+        validSig,
+        PUB_KEY_1, // not in pubkeys list
+      );
+      expect(valid).toBe(false);
+    });
+  });
+
+  describe('broadcastTransaction', () => {
+    it('should succeed with 2+ signatures', async () => {
+      const result = await adapter.broadcastTransaction(
+        'BTC',
+        { escrow_address: 'bc1qmultisig123' },
+        [
+          { pubkey: PUB_KEY_1, signature: 'sig1' },
+          { pubkey: PUB_KEY_2, signature: 'sig2' },
+        ],
+      );
+
+      expect(result.success).toBe(true);
+      expect(result.tx_hash).toBeTruthy();
+    });
+
+    it('should fail with fewer than 2 signatures', async () => {
+      const result = await adapter.broadcastTransaction(
+        'BTC',
+        { escrow_address: 'bc1qmultisig123' },
+        [{ pubkey: PUB_KEY_1, signature: 'sig1' }],
+      );
+
+      expect(result.success).toBe(false);
+    });
+  });
+});