Implement an ERC-4337 v0.7 SimpleAccount and VerifyingPaymaster in the two listed files, following eth-infinitism account-abstraction v0.7.0. Do not deploy. Workspace: the job starts from an empty tree (no foundry.toml, forge-std or OpenZeppelin) and each worker may write only the listed src files and their test/.t.sol files, so no dependency can be added. Write everything inline (pragma ^0.8.24, default forge layout, no imports beyond these files); mocks and helper contracts live inside the test files, which declare the cheatcodes they use in an inline Vm interface at the HEVM address and assert with require.

Types, declared inline: PackedUserOperation {address sender; uint256 nonce; bytes initCode; bytes callData; bytes32 accountGasLimits; uint256 preVerificationGas; bytes32 gasFees; bytes paymasterAndData; bytes signature}, plus the IAccount, IPaymaster and IEntryPoint deposit/stake functions used.

SimpleAccount: constructor(address entryPoint, address owner), both immutable and nonzero; no proxy or initializer. validateUserOp(userOp, userOpHash, missingAccountFunds), EntryPoint only: recover the signer of the EIP-191 eth-signed userOpHash with an inline ecrecover that rejects high s and lengths other than 65; return 0 for the owner and 1 (SIG_VALIDATION_FAILED) otherwise, never reverting on a bad signature; then send missingAccountFunds to the EntryPoint. execute(dest, value, func) and executeBatch(address[] dest, uint256[] value, bytes[] func), EntryPoint or owner only, bubble revert data; executeBatch is all-or-nothing, an empty value array means zero values, mismatched lengths revert. Nonces live in the EntryPoint. receive(); addDeposit() payable by anyone; getDeposit(); withdrawDepositTo(address, uint256) owner only.

VerifyingPaymaster: constructor(address entryPoint, address verifyingSigner, address owner). paymasterAndData = paymaster (20 bytes) | paymasterVerificationGasLimit (16) | paymasterPostOpGasLimit (16) | abi.encode(uint48 validUntil, uint48 validAfter) (64) | signature (64 or 65). getHash(userOp, validUntil, validAfter) = keccak256(abi.encode(sender, nonce, keccak256(initCode), keccak256(callData), accountGasLimits, uint256(bytes32(paymasterAndData[20:52])), preVerificationGas, gasFees, block.chainid, address(this), validUntil, validAfter)), signed as an EIP-191 message. validatePaymasterUserOp (EntryPoint only) returns empty context and validationData = sigFailed | uint256(validUntil) << 160 | uint256(validAfter) << 208 (validUntil 0 = no expiry); a wrong signer gives sigFailed = 1 without reverting, a paymasterAndData length other than 180 or 181 bytes reverts. No postOp logic. Owner only: setVerifyingSigner (event) and the EntryPoint deposit/stake calls (deposit, withdrawTo, addStake, unlockStake, withdrawStake).

Tests: test/SimpleAccount.t.sol holds a minimal test EntryPoint (test/VerifyingPaymaster.t.sol imports it) that computes userOpHash = keccak256(abi.encode(keccak256(the packed fields, dynamic ones hashed), address(entryPoint), block.chainid)), keeps nonces and deposits, rejects ops whose validationData fails or is outside its time window, and runs validateUserOp, validatePaymasterUserOp, the call and the refund in that order. Cover: a sponsored op end to end; a wrong account signature returns 1; a paymaster signature made for another chainId, paymaster, sender or nonce fails; the validUntil/validAfter window; replay fails on the nonce; non-EntryPoint callers of both validate functions revert; a stranger calling execute reverts; executeBatch reverts as a whole.

Review focus: signature replay across chains and paymasters, paymasterAndData offsets, returning instead of reverting on bad signatures, the missingAccountFunds payment, owner versus EntryPoint entry points, and any way a sponsored op drains the paymaster's deposit.