Add fromSeed function to SLIP10Node, BIP44Node, BIP44CoinTypeNode

[Mrtenz]

This adds a new function to initialise a key-tree node from a BIP-39 seed. This can be used to skip the step from mnemonic phrase to seed, and can improve performance if the seed is already available.

This function is only supported for secp256k1 and ed25519 for now. ed25519Bip32 may be added in the future.

Closes #210

[Copilot]

PR Overview

This PR introduces a new "fromSeed" function for SLIP10Node, BIP44Node, and BIP44CoinTypeNode that allows initializing a key-tree node directly from a seed rather than from a mnemonic phrase. It updates tests and internal derivation logic to use a Uint8Array seed when available and adjusts types and error messages accordingly.

• Adds a direct seed-based initialization method for hierarchical nodes.
• Updates test fixtures and related tests to use the seed value.
• Adjusts utility and conversion functions to support seed-based derivation.

Reviewed Changes

File	Description
src/BIP44CoinTypeNode.test.ts	Adds tests for initializing a BIP44CoinTypeNode from a seed, including custom crypto support
src/BIP44Node.test.ts	Adds tests for initializing a BIP44Node from a seed and updates path inputs from mnemonic to seed
src/utils.ts	Updates utility functions and types to support seed-based derivation
src/derivers/bip39.ts	Updates derivation functions to use a Uint8Array seed when provided
src/derivers/bip39.test.ts	Adds tests for getDerivationPathWithSeed and updates paths to use seed conversions
src/SLIP10Node.ts	Adds a new static async fromSeed method and updates the derivation logic accordingly
src/BIP44CoinTypeNode.ts	Adds a fromSeed static method using the new derivation function
src/BIP44Node.ts	Adds a fromSeed static method and updates derivation path validations
src/derivation.test.ts	Updates many tests to use seed inputs and getDerivationPathWithSeed for key derivation
test/fixtures.ts	Adds a seed fixture computed from the mnemonic
test/reference-implementations.test.ts	Updates reference tests with new seed-based derivation method
src/constants.ts	Adds new type definitions to differentiate seed-based derivation paths
src/SLIP10Node.test.ts	Updates tests to use fixtures.local.seed and new error messages for fromSeed

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (2)

src/SLIP10Node.ts:430

• Ensure that the derivationPath passed to fromSeed is already in seed format (i.e. its first element is a Uint8Array) as expected, or consider invoking getDerivationPathWithSeed for additional conversion to enforce consistency with fromDerivationPath.

static async fromSeed({ derivationPath, network, curve }: SLIP10DerivationPathOptions, cryptographicFunctions?: CryptographicFunctions): Promise<SLIP10Node> {

src/BIP44CoinTypeNode.ts:175

• [nitpick] Since the expected derivation path for a coin type node should have exactly three segments (seed, purpose, and coin type), consider explicitly validating that derivationPath.length is exactly 3 instead of using (derivationPath.length - 1) for depth validation.

static async fromSeed({ derivationPath, network }: BIP44CoinTypeSeedOptions, cryptographicFunctions?: CryptographicFunctions): Promise<BIP44CoinTypeNode> {

[FrederikBolding]

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