fix(committor): propagate tx assembly errors in prepare_for_strategy

Replace .expect() with ? so assembly failures return an error instead
of panicking the committor worker.
Fixes #1018

Author: crazywriter1

magicblock-committor-service/src/transaction_preparator/mod.rs

@@ -101,16 +101,14 @@ impl TransactionPreparator for TransactionPreparatorImpl {
             .await?;
         metrics::observe_committor_intent_alt_count(lookup_tables.len());
 
-        let message =
-            TransactionUtils::assemble_tasks_tx_with_uniqueness_nonce(
-                authority,
-                &tx_strategy.optimized_tasks,
-                self.compute_budget_config.compute_unit_price,
-                &lookup_tables,
-                tx_strategy.uniqueness_nonce,
-            )
-            .expect("Possibility to assemble checked above")
-            .message;
+        let message = TransactionUtils::assemble_tasks_tx_with_uniqueness_nonce(
+            authority,
+            &tx_strategy.optimized_tasks,
+            self.compute_budget_config.compute_unit_price,
+            &lookup_tables,
+            tx_strategy.uniqueness_nonce,
+        )?
+        .message;
 
         Ok(message)
     }