[#475] Builder Code (ERC-8021) attribution

[realproject7]

Parent: #475

Summary

Set up Builder Code attribution so all onchain transactions from PlotLink include the builder code suffix, earning Base builder rewards.

Context

From Dropcast issues #286, #288, #290:

• Do NOT manually append builder code to calldata — modern wallets wrap transactions internally
• Use EIP-5792 dataSuffix capability on wallet_sendCalls
• Fallback to direct sendTransaction with manual append only if wallet lacks EIP-5792

Steps

1. Register Builder Code

• OPERATOR: Register at base.dev to get a builder code (e.g., bc_xxxxxxxx)
• Add NEXT_PUBLIC_BUILDER_CODE to env vars

2. Create builder-code helper

Reference: ~/Projects/dropcast/lib/builder-code.ts

import { Attribution } from '@base/attribution';
const BUILDER_CODE = process.env.NEXT_PUBLIC_BUILDER_CODE ?? '';
export const DATA_SUFFIX = BUILDER_CODE ? Attribution.toDataSuffix({ codes: [BUILDER_CODE] }) : null;

3. Integrate with wagmi

Reference: ~/Projects/dropcast/lib/wagmi.ts

• Configure wagmi to use dataSuffix capability when available
• Primary: wallet_sendCalls with capabilities.dataSuffix
• Fallback: direct sendTransaction with manual append

4. Apply to all transaction paths

• TradingWidget: buy (ETH/USDC/HUNT/PLOT) and sell
• Create storyline
• Chain plot
• Donate
• Claim royalties

5. Verify attribution

• After a test tx, check via Base Attribution Checker that the builder code is detected

Dependencies

• @base/attribution npm package

Acceptance Criteria

• Builder code registered (operator gate)
• DATA_SUFFIX generated from builder code
• All tx paths include builder code attribution
• Verified via Attribution Checker on at least one tx
• Fallback works for wallets without EIP-5792

Branch

task/475-builder-code in plotlink repo