Fix Uniswap V4 Universal Router encoding for three-action swap flow

[Copilot]

The V4 swap implementation incorrectly encoded commands and inputs as a single action instead of the required three-step flow (swap → settle → take) that V4's PoolManager architecture requires.

Changes

Contract Updates (EtherTrialsTRIAv5_Simple.sol)

• Added IUniversalRouter interface and immutable state variable
• Added V4 command constants: V4_SWAP (0x00), SETTLE (0x09), TAKE (0x0a)
• Extended constructor to accept _universalRouter address
• Implemented _swapETHToTRIAV4() with proper command/input encoding

Key Fix:

// Three commands, three inputs (not 1:1)
bytes memory commands = abi.encodePacked(V4_SWAP, SETTLE, TAKE);
bytes[] memory inputs = new bytes[](3);

// Each command gets its own encoded parameters
inputs[0] = abi.encode(recipient, amountIn, minOut, path, payerIsUser);
inputs[1] = abi.encode(currency, amount, payerIsUser);
inputs[2] = abi.encode(currency, recipient, amount);

universalRouter.execute{value: ethAmount}(commands, inputs);

Documentation

• V4_SWAP_ENCODING_EXPLAINED.md - Technical breakdown of encoding structure
• SECURITY_SUMMARY.md - Security analysis (no vulnerabilities identified)
• V4_INTEGRATION_GUIDE.md - Deployment and usage reference
• IMPLEMENTATION_SUMMARY.md - Complete implementation overview

Deployment

Base Mainnet Universal Router: 0x6ff5693b99212da76ad316178a184ab56d299b43

Note: Constructor signature changed - requires Universal Router address parameter. Existing deployments incompatible due to immutable state.

Original prompt

Fix Uniswap V4 Universal Router encoding error in _swapETHToTRIAV4 function. The main issues are:

1. The inputs array structure is incorrect - combining actions and params into a single element when it should be properly encoded
2. The command/inputs mismatch - 1 command with 1 input containing multiple sub-actions needs proper encoding
3. The parameter encoding for V4 swap doesn't match Universal Router expectations

The fix should:

• Properly encode the V4_SWAP command with correct input structure
• Use the correct ABI encoding format that Universal Router expects
• Ensure commands and inputs array lengths/structure match
• Handle the three sequential actions (swap, settle, take) with proper encoding

This pull request was created as a result of the following prompt from Copilot chat.

Fix Uniswap V4 Universal Router encoding error in _swapETHToTRIAV4 function. The main issues are:

1. The inputs array structure is incorrect - combining actions and params into a single element when it should be properly encoded
2. The command/inputs mismatch - 1 command with 1 input containing multiple sub-actions needs proper encoding
3. The parameter encoding for V4 swap doesn't match Universal Router expectations

The fix should:

• Properly encode the V4_SWAP command with correct input structure
• Use the correct ABI encoding format that Universal Router expects
• Ensure commands and inputs array lengths/structure match
• Handle the three sequential actions (swap, settle, take) with proper encoding

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