feat: add Solana signer abstraction layer

[fengtality]

Summary

This PR introduces a pluggable signer abstraction layer for Solana, modeled after the @solana/keychain library patterns. The abstraction provides a unified interface for signing transactions regardless of wallet type (hot wallet, hardware wallet, or future integrations like AWS KMS).

Relationship to @solana/keychain

The @solana/keychain library from the Solana Foundation provides a standardized signer abstraction for the Solana ecosystem. However, it is not yet published to npm and uses the new @solana/kit (v2) SDK which would require a significant migration from our current @solana/web3.js (v1) implementation.

This PR implements the same patterns and interfaces from @solana/keychain-core adapted for @solana/web3.js v1:

• SolanaSigner interface - Matches keychain-core's unified signer interface with signTransactions(), signMessages(), isAvailable(), and address properties
• SignerErrorCode enum - Uses SIGNER_ prefixed codes matching keychain-core (e.g., SIGNER_SIGNING_FAILED, SIGNER_NOT_AVAILABLE)
• Utility functions - Implements keychain-core patterns:
  • createSignerError() / throwSignerError() - Error creation helpers
  • isSolanaSigner() / assertIsSolanaSigner() - Type guards

When @solana/keychain is published to npm, we can migrate to use it directly with minimal changes.

Key Changes

• New signer interface and implementations (src/chains/solana/signers/)

  • SolanaSigner interface with standardized methods for signing
  • KeypairSigner for hot wallets (encrypted keypair files)
  • LedgerSigner for hardware wallets (wraps existing HardwareWalletService)
  • SignerFactory for automatic wallet type detection

• Solana chain enhancements (src/chains/solana/solana.ts)

  • Added getSigner(address) method to get appropriate signer for any wallet
  • Added signAndSend(transaction, signer, options) for unified transaction signing and submission
  • Support for additionalKeypairs option for multi-signer transactions (e.g., new position accounts)
  • Updated getBalance to accept PublicKey in addition to Keypair

• Jupiter connector update (src/connectors/jupiter/)

  • Added buildUnsignedSwapTransaction() method
  • Simplified executeQuote route using new signer pattern

• Meteora connector update (src/connectors/meteora/clmm-routes/)

  • Updated all CLMM routes to use signer abstraction:
    • addLiquidity - now supports hardware wallets
    • removeLiquidity - now supports hardware wallets
    • openPosition - now supports hardware wallets (with additionalKeypairs for position account)
    • closePosition - now supports hardware wallets
    • collectFees - now supports hardware wallets
    • executeSwap - now supports hardware wallets

Benefits

1. Wallet-agnostic signing - Connectors don't need to check wallet type or implement separate code paths
2. Simplified connector code - Jupiter executeQuote reduced from ~30 lines to ~10 lines
3. Extensible - Easy to add AWS KMS, Fireblocks, Turnkey, Privy, or other signers in the future
4. Unified error handling - Consistent SignerError with error codes across all implementations
5. Hardware wallet support - All Meteora and Jupiter operations now work with Ledger devices
6. Future-proof - Interface compatible with @solana/keychain for easy migration when available

Usage Example

// Old pattern (connector must handle wallet types)
const isHardware = await solana.isHardwareWallet(address);
if (isHardware) {
  const tx = await connector.buildTxForHardwareWallet(...);
  const ledger = new SolanaLedger();
  tx = await ledger.signTransaction(address, tx);
  // ... send
} else {
  const wallet = await solana.getWallet(address);
  const tx = await connector.buildSwapTransaction(wallet, ...);
  // ... send
}

// New pattern (simplified)
const signer = await solana.getSigner(walletAddress);
const tx = await connector.buildUnsignedTransaction(...);
const result = await solana.signAndSend(tx, signer);

// For transactions needing additional signers (e.g., new position account)
const newPosition = new Keypair();
const result = await solana.signAndSend(tx, signer, {
  additionalKeypairs: [newPosition]
});

Test plan

• Run signer unit tests: GATEWAY_TEST_MODE=dev npx jest test/chains/solana/signers/ (32 passed)
• Run Jupiter connector tests: GATEWAY_TEST_MODE=dev npx jest test/connectors/jupiter/ (25 passed)
• Run Solana chain tests: GATEWAY_TEST_MODE=dev npx jest test/chains/solana/ (102 passed)
• Run Meteora connector tests: GATEWAY_TEST_MODE=dev npx jest test/connectors/meteora/ (44 passed)
• TypeScript typecheck passes
• Manual testing with hot wallet swap
• Manual testing with Ledger hardware wallet swap (if available)

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