fix(envelope): split abi.encode to avoid viaIR, add deploy+verify scripts

[aliXsed]

Summary

Fixes ZkSync source verification for EnvelopeLinks by eliminating the need for viaIR compilation, and adds reproducible deploy+verify scripts.

Problem

EnvelopeLinks._feeAuthorizationDigest had 15 parameters in a single abi.encode() call, exceeding solc's stack limit without viaIR. The ZkSync verifier cannot handle viaIR contracts:

• zksolc ≤1.5.1: ignores viaIR flag → stack-too-deep error
• zksolc ≥1.5.13: passes viaIR through → internal error (verifier crashes)

Solution

Split the abi.encode into two parts joined by abi.encodePacked:

// abi.encodePacked(abi.encode(a..h), abi.encode(i..n)) == abi.encode(a..n)
// because abi.encode pads each value to 32 bytes

This produces byte-identical output and preserves EIP-712 signature compatibility while compiling without viaIR.

Changes

File	Change
src/envelope/EnvelopeLinks.sol	Split _feeAuthorizationDigest abi.encode (8+7 params)
ops/verify_hardhat_zksync.py	New: verification script for Hardhat builds (BFS imports, filtered standard JSON, API submission)
ops/deploy_envelope_zksync.sh	New: one-command Hardhat deploy + verify workflow
hardhat-deploy/DeployEnvelope.ts	Auto-select .env-prod on mainnet
src/envelope/doc/EnvelopeLinks.md	Document fee-on-transfer token restriction
.github/copilot-instructions.md	Document Hardhat path, split trick, and verification workflow

Deployed & Verified (ZkSync Era Mainnet)

Contract	Address	Status
EnvelopeLinks	0xff735c70f33ca4eF1768F527B5f230b76A61A89b	✅ Fully verified
EnvelopePaymaster	0x5396e4F349D863C0AD577bd9E752293524460C36	✅ Fully verified

Paymaster is not funded — will be funded separately after review.

Testing

• All 8 EnvelopeLinks unit tests pass
• All 19 EIP712 tests pass (18 pass, 1 pre-existing fuzz issue unrelated to this change)
• All 7 integration tests pass
• yarn spellcheck: 0 issues

[github-actions]

LCOV of commit fee57f3 during checks #713

Summary coverage rate:
  lines......: 25.7% (771 of 3001 lines)
  functions..: 22.3% (105 of 470 functions)
  branches...: 27.5% (140 of 509 branches)

Files changed coverage rate:
                                                  |Lines       |Functions  |Branches    
  Filename                                        |Rate     Num|Rate    Num|Rate     Num
  ======================================================================================
  src/envelope/EnvelopeLinks.sol                  | 0.0%    355| 0.0%    53| 0.0%     96