fix: decode the fork ID as a list

[MegaRedHand]

This PR decodes the fork ID of a node record's "eth" entry as a list. Previously, we were assuming the list was small enough to have a length of a single byte.

[Copilot]

Pull Request Overview

This PR updates the eth fork ID decoding to use a proper RLP list decoder and tidies up the RLP decoder struct.

• Swap single-byte-slice decode for Decoder::new + decode_optional_field in NodeRecord’s eth branch
• Add blank-line spacing before get_encoded_item in RLP decoder for readability

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
crates/networking/p2p/types.rs	Replaced manual slice decode of fork ID with RLP Decoder logic
crates/common/rlp/structs.rs	Inserted spacing before get_encoded_item method for consistent layout

Comments suppressed due to low confidence (2)

crates/networking/p2p/types.rs:270

• [nitpick] Add a brief comment explaining that this decodes the outer RLP list and extracts an optional fork ID field, replacing the previous single-byte assumption.

                    let Ok(decoder) = Decoder::new(&value) else {

crates/common/rlp/structs.rs:69

• Add unit tests for get_encoded_item to verify it returns the correct byte slice and handles error cases as expected.

    /// Returns the next field without decoding it, i.e. the payload bytes including its prefix.

[Copilot]

Consider using decoder.finish() (which returns a Result) instead of finish_unchecked() to catch any leftover bytes or malformed input.

Suggested change

	decoder.finish_unchecked();
	decoded_pairs.eth = fork_id;
	match decoder.finish() {
	Ok(_) => decoded_pairs.eth = fork_id,
	Err(_) => continue,
	}

[github-actions]

Lines of code report

Total lines added: 15
Total lines removed: 1
Total lines changed: 16

Detailed view

+-------------------------------------------------+-------+------+
| File                                            | Lines | Diff |
+-------------------------------------------------+-------+------+
| ethrex/crates/l2/prover/zkvm/interface/build.rs | 68    | -1   |
+-------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/types.rs           | 444   | +5   |
+-------------------------------------------------+-------+------+
| ethrex/crates/vm/backends/levm/mod.rs           | 548   | +5   |
+-------------------------------------------------+-------+------+
| ethrex/crates/vm/backends/revm/mod.rs           | 568   | +5   |
+-------------------------------------------------+-------+------+