feat: CoW TWAP ExtensibleFallbackHandler verification + inline hardhat config

[tamtamchik]

Summary

• Add diffyscan config for verifying the CoW Protocol ExtensibleFallbackHandler at 0x2f55e8b20D0B9FEFA187AA7d00B6Cbe563605bF5 — source (26/26 files identical) and bytecode fully match
• Add support for inline hardhat_config in JSON configs, so separate .ts files are no longer required for bytecode comparison
• Update README with inline hardhat config documentation

Details

CoW TWAP verification config

Verifies the ExtensibleFallbackHandler deployed for CoW Protocol TWAP orders against:

• Parent repo: cowprotocol/composable-cow @ ab3addad
• EFH submodule: cowdao-grants/extensible-fallback-handler @ e53ffea4
• OpenZeppelin v4.9.3

Inline hardhat config

New bytecode_comparison.hardhat_config JSON field that auto-generates a temporary Hardhat config at runtime:

"hardhat_config": {
  "solidity_version": "0.8.19",
  "optimizer": true,
  "optimizer_runs": 20000
}

Chain ID is taken from explorer_chain_id. Temp file is cleaned up after the run. Existing hardhat_config_name and --hardhat-path continue to work.

Test plan

• Source comparison: 26/26 files identical, 0 diffs
• Bytecode comparison: bytecodes fully match
• Inline hardhat config generates and cleans up correctly
• Existing --hardhat-path CLI flag still works
• Existing hardhat_config_name in JSON still works

[Copilot]

Pull request overview

Adds a new verification config for CoW Protocol’s TWAP ExtensibleFallbackHandler and introduces support for embedding Hardhat settings directly in JSON configs by generating a Hardhat config file at runtime.

Changes:

• Generate a Hardhat .ts config from inline bytecode_comparison.hardhat_config settings and clean it up after the run.
• Add a new sample config to verify CoW TWAP’s ExtensibleFallbackHandler deployment on Ethereum mainnet.
• Document inline Hardhat config usage and supported fields in the README.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
diffyscan/utils/hardhat.py	Adds generate_hardhat_config() to emit a Hardhat config from JSON settings.
diffyscan/diffyscan.py	Resolves Hardhat config path via inline config or hardhat_config_name, and cleans up generated config.
config_samples/ethereum/mainnet/cow_twap/cow_twap_extensible_fallback_handler.json	New sample config for verifying CoW TWAP EFH deployment and bytecode match.
README.md	Documents inline hardhat_config and updates usage instructions.

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[TheDZhon]

no longer hardhatting here 👷 ❌

[TheDZhon]

GG, but some small qs

[TheDZhon]

why though?

[TheDZhon]

is it audited?

[TheDZhon]

audit?