environmentd: fix test_dataflow_error_codes setup and format branch code

`test_dataflow_error_codes` issued `CREATE TABLE` and `INSERT` in a
single `batch_execute`, which forms an implicit transaction block; DDL
cannot run inside one, so the test failed at setup with E25001. Run the
statements separately.

Also apply `cargo fmt` to the `PeekError` call sites introduced earlier
on this branch.

Author: antiguru

src/compute-client/src/controller/instance.rs

@@ -1221,9 +1221,9 @@ impl Instance {
             self.deliver_response(response);
         }
         for uuid in to_drop {
-            let response = PeekResponse::Error(
-                crate::protocol::response::PeekError::internal(ERROR_TARGET_REPLICA_FAILED),
-            );
+            let response = PeekResponse::Error(crate::protocol::response::PeekError::internal(
+                ERROR_TARGET_REPLICA_FAILED,
+            ));
             self.finish_peek(uuid, response);
         }
 

src/compute/src/compute_state.rs

@@ -1591,7 +1591,9 @@ impl IndexPeek {
                 // Preserve the structured dataflow error so the adapter can
                 // assign a precise SQLSTATE instead of a generic internal error.
                 let error = cursor.key(&storage).deserialize();
-                return PeekStatus::Ready(PeekResponse::Error(PeekError::Dataflow(Box::new(error))));
+                return PeekStatus::Ready(PeekResponse::Error(PeekError::Dataflow(Box::new(
+                    error,
+                ))));
             }
             cursor.step_key(&storage);
         }

src/environmentd/tests/sql.rs

@@ -2382,9 +2382,12 @@ fn test_dataflow_error_codes() {
 
     // Referencing a table column keeps the optimizer from constant-folding the
     // failing expression, so the error is produced during dataflow execution.
+    // Run the DDL and DML separately: a multi-statement batch forms an implicit
+    // transaction block, and `CREATE TABLE` cannot run inside one.
     client
-        .batch_execute("CREATE TABLE t (a int4, b int4); INSERT INTO t VALUES (1, 0);")
+        .batch_execute("CREATE TABLE t (a int4, b int4)")
         .unwrap();
+    client.batch_execute("INSERT INTO t VALUES (1, 0)").unwrap();
 
     let cases: &[(&str, &SqlState)] = &[
         // Division by zero over a collection -> division_by_zero (22012).