BIP-39/BIP-32 mnemonic derivation implemented but not tested

Problem

The codebase has BIP-39 mnemonic and BIP-32 HD key derivation implementation, but there are no tests verifying correctness against standard test vectors.

Location

src/protocol/account.ts - mnemonic-related functions

Risk

• Implementation bugs could generate wrong keys
• Users could lose funds if derivation is incorrect
• No verification against BIP-39/BIP-32 test vectors

Recommendation

1. Add tests using official BIP-39 test vectors
2. Add tests using official BIP-32 test vectors
3. Test edge cases (invalid mnemonics, hardened vs non-hardened paths)

// Example test vectors from BIP-39
const TEST_VECTORS = [
  {
    mnemonic: 'abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about',
    seed: '5eb00bbddcf069084889a8ab9155568165f5c453ccb85e70811aaed6f6da5fc19a5ac40b389cd370d086206dec8aa6c43daea6690f20ad3d8d48b2d2ce9e38e4',
    // ... derived keys
  }
];

Priority

Medium - Security-critical code path

Read the mnemonic-related functions in src/protocol/account.ts and compare their behavior with the official BIP-39 and BIP-32 test vectors. Add coverage for valid vectors, invalid mnemonics, and hardened versus non-hardened paths. Done means the implementation matches the published vectors and the listed edge cases are verified by tests.