claude: address third round of review feedback

- Downgrade error! to debug! for best-effort delivery tx storage
- Fix idempotency: store_message_with_dispatch_tx now returns actual
  store_message result and only stores dispatch tx mapping for new messages
- Remove unused warn import from hyperlane_db.rs
- Fix spurious blank lines in hyperlane_db.rs and contract_sync/mod.rs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: danwt

rust/main/agents/relayer/src/msg/pending_message.rs

@@ -925,13 +925,13 @@ impl PendingMessage {
         if let Some(outcome) = &self.submission_outcome {
             let message_id = self.message.id();
 
-            // Store on destination: message_id -> tx_hash (for /delivered endpoint)
+            // Best-effort: store delivery tx hash for /delivered endpoint
             if let Err(e) = self
                 .ctx
                 .destination_db
                 .store_delivery_tx(&message_id, &outcome.transaction_id)
             {
-                error!(
+                debug!(
                     message_id = ?message_id,
                     tx_id = ?outcome.transaction_id,
                     destination = ?self.message.destination,

rust/main/hyperlane-base/src/contract_sync/mod.rs

@@ -96,7 +96,6 @@ where
         self.broadcast_sender.clone()
     }
 
-
     /// Sync logs and write them to the LogStore
     #[instrument(name = "ContractSync", fields(domain=self.domain().name()), skip(self, opts))]
     pub async fn sync(&self, label: &'static str, opts: SyncOptions<T>) {

rust/main/hyperlane-base/src/db/rocks/hyperlane_db.rs

@@ -2,8 +2,7 @@ use std::ops::Add;
 
 use async_trait::async_trait;
 use eyre::{bail, Result};
-use tracing::{debug, instrument, trace, warn};
-
+use tracing::{debug, instrument, trace};
 
 use hyperlane_core::{
     identifiers::UniqueIdentifier, Decode, Encode, GasPaymentKey, HyperlaneDomain,
@@ -82,18 +81,20 @@ impl HyperlaneRocksDB {
     }
 
     /// Store a message with its dispatch transaction ID.
+    /// Returns true if the message was newly stored, false if it already existed.
     pub fn store_message_with_dispatch_tx(
         &self,
         message: &HyperlaneMessage,
         dispatched_block_number: u64,
         dispatch_tx_id: &H512,
     ) -> DbResult<bool> {
-        self.store_message(message, dispatched_block_number)?;
-        self.store_message_id_by_dispatch_tx(dispatch_tx_id, &message.id())?;
-        Ok(true)
+        let newly_stored = self.store_message(message, dispatched_block_number)?;
+        if newly_stored {
+            self.store_message_id_by_dispatch_tx(dispatch_tx_id, &message.id())?;
+        }
+        Ok(newly_stored)
     }
 
-
     /// Store a raw committed message. If message already exists, then do nothing.
     ///
     /// Keys --> Values: