feat(sdk-coin-sol): implement deriveAddress for SOL

[rajangarg047]

Summary

Implements deriveAddress for SOL (Stage A — MPC/TSS), overriding the BaseCoin default. It locally derives a Solana receive address from the wallet's commonKeychain + index, reusing the shared deriveMPCWalletAddress (ed25519) helper. Offline and key-material-free (public keys only); supports the SMC prefix path via derivedFromParentWithSeed.

This is the inverse of isWalletAddress and shares its exact derivation path (deriveMPCWalletAddress), so derive and verify can never diverge.

Context

Part of FR-465 (Bullish local address derivation), Phase 1 Stage A. Builds only on the already-merged primitive (WCN-912) and shared MPC engine (WCN-913) — independent of the Express endpoint (WCN-914) and the other coin PRs.

• Linear: WCN-917 (child of WCN-864)

Test plan

• tsc --noEmit clean for sdk-coin-sol
• eslint clean (0 errors)
• 5 new deriveAddress unit tests pass: exact-vector derivation, distinct address per index, derive→verify round-trip, SMC-seed round-trip, and missing-keychains error. Reuses the existing isWalletAddress test vector.
• CI

🤖 Generated with Claude Code

[linear-code]

WCN-917

[rajangarg047]

@claude

[github-actions]

Claude finished @rajangarg047's task —— View job

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Code Review Complete ✅

• Read repository guidelines (CLAUDE.md)
• Review implementation in sol.ts
• Review test coverage in sol.ts test file
• Check code quality and best practices
• Provide comprehensive feedback

Summary

This PR successfully implements deriveAddress for SOL (Solana), providing local address derivation from wallet keychains. The implementation is well-structured and follows BitGoJS patterns.

✅ Strengths

1. Excellent Documentation: The method includes comprehensive JSDoc explaining its purpose, relationship to isWalletAddress, and guarantees about derivation consistency.

2. Proper Integration: Correctly imports and uses the shared deriveMPCWalletAddress helper from @bitgo/sdk-core, maintaining consistency with the existing codebase architecture.

3. Complete Test Coverage: The test suite includes 5 comprehensive scenarios:

   • Exact vector derivation test using known commonKeychain → address
   • Different indices produce different addresses
   • Critical round-trip test: derive → verify ensures the methods never diverge
   • SMC seed support with round-trip verification
   • Error handling for missing keychains

4. Type Safety: Proper TypeScript usage with correct imports of DeriveAddressOptions and DeriveAddressResult interfaces.

5. Consistent with Existing Code: Reuses the existing getAddressFromPublicKey helper, maintaining the same conversion logic used elsewhere.

🔍 Implementation Details

The implementation at modules/sdk-coin-sol/src/sol.ts:728-742 is concise and correct:

• Uses deriveMPCWalletAddress with proper parameters including keyCurve: 'ed25519'
• Delegates address conversion to existing getAddressFromPublicKey method
• Returns the expected DeriveAddressResult format
• Handles both regular derivation and SMC seed-based derivation

⚠️ Minor Observations

1. Runtime Validation: The comment mentions "extractCommonKeychain validates the commonKeychain is present at runtime" but this validation happens within deriveMPCWalletAddress, which is correct.

2. Error Propagation: The implementation correctly lets deriveMPCWalletAddress handle validation and error cases, maintaining consistency with the shared helper's error handling.

🎯 Architecture Alignment

This implementation perfectly aligns with the stated goal of being "the inverse of isWalletAddress" by:

• Using identical derivation paths (deriveMPCWalletAddress is shared)
• Using the same getAddressFromPublicKey conversion
• Supporting the same SMC seed functionality

The round-trip test in the test suite validates this guarantee, ensuring the two methods can never diverge.

Recommendation: ✅ APPROVE

This is a well-implemented, thoroughly tested feature that correctly integrates with the existing BitGoJS architecture. The code follows repository conventions, includes proper documentation, and maintains consistency with existing patterns.