fix: review fixes

Author: meyer9

Cargo.lock

@@ -31,3 +31,4 @@ async-trait.workspace = true
 eyre.workspace = true
 futures-util.workspace = true
 serde.workspace = true
+thiserror.workspace = true

crates/exex/external-proofs/Cargo.toml

@@ -1,13 +1,17 @@
-#![allow(dead_code, unreachable_pub)]
+#![expect(dead_code, unreachable_pub)]
 use alloy_primitives::{map::HashMap, B256, U256};
 use async_trait::async_trait;
 use auto_impl::auto_impl;
 use reth_primitives_traits::Account;
 use reth_trie::{updates::TrieUpdates, BranchNodeCompact, HashedPostState, Nibbles};
 use std::fmt::Debug;
+use thiserror::Error;
 
 /// Error type for storage operations
+#[derive(Debug, Error)]
 pub enum ExternalStorageError {
+    // TODO: add more errors once we know what they are
+    #[error("Other error: {0}")]
     Other(eyre::Error),
 }