BIP32-Ed25519 derivation used Node's crypto module (SHA-512, SHA-256,
HMAC-SHA512), bn.js and Buffer, which tie the published build to Node.
Replace them with the synchronous @noble/hashes functions, bigint arithmetic
via @noble/curves' byte helpers, and plain Uint8Array. fromSeed now accepts
any Uint8Array (a Buffer still works).

Key derivation, signatures and ECDH outputs are byte-identical. signData and
signAlgoTransaction now return a plain Uint8Array at runtime instead of a
Buffer (as in 1.x); the README's breaking changes list this.

bn.js is no longer a dependency. tsconfig.build.json sets "types": [] so the
published build fails to compile if it uses Node globals or built-ins, and CI
now runs pnpm build, since pnpm test compiles with Node types available.

README: the index-validation entry no longer mentions Buffer writes, lists
account among the validated arguments, and notes that fractional indexes
were silently truncated in 1.x.

- Note v5.3.0+ for rekeyed accounts and v5.4.0+ for appSecret in the
  guide, README, Supported Wallets and Signing Data
- State which rekeyed accounts the passkey signs for, and that it can't
  sign as one key of a multisig
- Document what withAppSecret returns and its `failed` case when the
  session locks mid-request
- Say plainly that users can export a recovery phrase, and link the
  use-wallet-ui react-passkey and vue-passkey examples

- Note v5.3.0+ for rekeyed accounts and v5.4.0+ for appSecret in the
  guide, README, Supported Wallets and Signing Data
- State which rekeyed accounts the passkey signs for, and that it can't
  sign as one key of a multisig
- Document what withAppSecret returns and its `failed` case when the
  session locks mid-request
- Say plainly that users can export a recovery phrase, and link the
  use-wallet-ui react-passkey and vue-passkey examples