[#470] Fix USDC zap mint: restore _encodeAsStruct for V4 multi-hop

[realproject7]

Summary

• Root cause: V4 Router's CalldataDecoder.decodeSwapExactInParams/decodeSwapExactOutParams reads the first word of action params as an offset pointer (swapParams := add(params.offset, calldataload(params.offset))). Our abi.encode(field1, field2, ...) produced a flat tuple (first word = address), but the decoder expects abi.encode(struct) format (first word = 0x20 offset).
• Previous fix (PR #469) correctly added _encodeAsStruct but also included noPriceChecks (uint256[]) matching the v4-periphery lib's new minHopPriceX36 field. The deployed Universal Router (Jan 2025) predates that field (added Nov 2025), corrupting the ABI layout.
• Fix: Restore _encodeAsStruct (adds 0x20 prefix) WITHOUT noPriceChecks
• Deployed new ZapPlotLinkV2: 0xAe50C9444DA2Ac80B209dC8B416d1B4A7D3939B0
• Successful mainnet USDC mint tx: 0x417378c8...

Test plan

• Fork test: USDC mintReverse (exact input) — PASS
• Fork test: USDC mint (exact output) — PASS
• Fork test: ETH mintReverse — PASS (no regression)
• Real mainnet tx: USDC mint 1000 tokens — SUCCESS
• Verify ETH and HUNT zap still work on new deployment
• Update plotlink app constants (separate PR)

Fixes realproject7/plotlink#470

🤖 Generated with Claude Code

[project7-interns]

Verdict: APPROVE

Summary

The contract change is narrowly scoped to the V4 multi-hop ABI layout regression and the deployment/docs updates are consistent with the new address. I did not find correctness, security, or scope issues in this diff.

Findings

• None.

Decision

Approve. The fix restores the struct-style encoding expected by the deployed Universal Router without reintroducing the incompatible extra field from PR #469.

[project7-interns]

T2b APPROVE

Fix is minimal, correct, and validated on mainnet.

• _encodeAsStruct correctly prepends 0x20 offset word for V4 Router's CalldataDecoder
• noPriceChecks field properly removed — incompatible with deployed Jan 2025 Universal Router
• Both swap directions (exact-in and exact-out) are fixed
• Helper is private pure, no security concerns
• No regression to ETH single-hop paths

Note (non-blocking): exact-in path uses uint128(0) as amountOutMinimum — slippage protection relies on downstream bonding curve check. Pre-existing, not introduced here.