fix: publish EIP-7702 code changes

[AshinGau]

Summary

• detect code changes by comparing the post-state code hash with the value read during execution
• publish the updated code hash and bytecode when an EIP-7702 authority is re-delegated
• add a regression test that compares sequential and parallel execution for two delegations followed by a call

Context

When an authority is delegated from contract X to contract Y later in the same block, its previous code hash is already non-empty. Treating code as new only when the previous hash is absent skips the second code publication, so a later transaction can resolve X instead of Y from multi-version memory.

The regression test makes the difference observable by having X and Y store different values in the authority account.

Tests

• cargo fmt --all -- --check
• RUSTFLAGS=-Dwarnings cargo clippy --workspace --all-targets
• cargo test -p pevm --lib
• cargo test --release -p pevm --test eip7702 -- --test-threads=1

Closes #518

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.