Summary

Rewrites the broken chain_sync.py stub into a working on-chain settlement module for credit issuance and retirement.

Changes

• Fixed sync_credits_to_chain(): correct ERC-1155 ABI, keccak256 tokenId derivation matching Solidity contract, actual web3 issue() transactions
• Added retire_onchain(): calls retire() on ERC-1155 contract for confirmed retirements
• Fixed verify_chain_balance(): uses ERC-1155 balanceOf (was incorrectly using EAS contract)
• Fixed reconcile_all(): real account addresses, correct token ID derivation
• Wired into flows: batch_manager.issue_batch() and carbon_credits.review_retirement()
• CLI subcommand: chain-sync with sync, retire-onchain, verify, and reconcile operations
• Generated ABI: contracts/abis/KokonutCreditToken.json

Safety

All on-chain calls gated by CREDIT_ONCHAIN_SYNC_ENABLED env var (default false). No behavioral change for existing deployments.

Tests

15 mocked web3 tests covering minting, retirement, balance verification, reconciliation, and token ID computation.