fix(TimelockPolicy): correct ERC-7579 no-op detection encoding

[leekt]

Summary

Fixes TOB-KERNEL-18 (Informational): No-op detection for ERC-7579 execute is inconsistent with actual encoding.

• Offset fix: _isNoOpERC7579Execute now checks offset 64 (2 ABI head slots) instead of 32
• Compact format fix: ERC-7579 decodeSingle uses abi.encodePacked(target, value, calldata) with no explicit length prefix. No-op detection now checks execDataLength == 52 (target 20B + value 32B, no inner calldata) instead of looking for a separate calldataLength word
• Updated BTT tests to use correct ABI encoding and compact execution format

Audit Reference

• Finding: TOB-KERNEL-18 — No-op detection for ERC-7579 execute is inconsistent with actual encoding
• Severity: Informational
• Auditor: Trail of Bits (Offchain Labs Kernel v4 Security Assessment, January 2026)

Test plan

• Valid no-op (target=self, value=0) detected correctly
• Valid no-op (target=address(0), value=0) detected correctly
• Wrong offset (not 64) rejected
• execDataLength != 52 rejected
• execDataLength > 52 (has inner calldata) rejected
• Wrong target rejected
• Non-zero value rejected
• Short calldata rejected