fix(hyperliquid): support builder order attribution

[BridgeAISocial]

Summary

• add optional Hyperliquid builder / builderFee order params
• include action.builder = { b, f } in the signed raw order payload before submit
• document the new params in OpenAPI/API reference output
• add regression coverage for builder attribution and malformed builder params

Verification

• npm --workspace=pmxt-core test -- hyperliquid-build-order.test.ts
• npm --workspace=pmxt-core run build
• npm --workspace=pmxt-core test — 48 suites passed, 1 skipped; 812 passed, 3 skipped
• safe no-spend build check: PMXT buildOrder raw payload now includes builder:{b:"0x370a6d37911294ebe8d45419d007e7e0c4bec2a9",f:10}

Testnet faucet status

The PMXT-side builder attribution blocker is fixed in this PR. The remaining funded testnet execution blocker is external funding/deposit state: Hyperliquid testnet rejects approve/order actions for the throwaway wallet with Must deposit before performing actions / User or API Wallet ... does not exist. Rechecked the Hyperliquid testnet USDC drip contract: claimDrip() gas estimation succeeds, but the throwaway wallet has 0.0 Arbitrum Sepolia ETH for gas.