fix(pgwire): reject incomplete multi-statement batches with hard error

B1 (2026-08-26): batches >32 statements silently dropped the tail
(batch 64 landed 32, batch 128 landed ~25%) with no error — clients
believed work committed. Now any short response count returns XX000
'incomplete batch' so the client retries with a smaller batch.
Defense-in-depth until the propose-path drop site is traced.

Author: EnRaiha

nodedb/src/control/server/pgwire/handler/sql_exec.rs

@@ -43,11 +43,31 @@ impl NodeDbPgHandler {
                     .await
             }
             _ => {
+                let total = statements.len();
                 let mut all = Vec::new();
                 for stmt in statements {
                     let mut resp = self.execute_single_sql(identity, session_id, &stmt).await?;
                     all.append(&mut resp);
                 }
+                // B1 ack reconciliation (2026-08-26): every statement must
+                // produce at least one response. A short count means the
+                // executor silently dropped work (observed: batch 64 → 32
+                // landed, batch 128 → ~25%, no error). Surface it as a hard
+                // error instead of letting the client believe the batch
+                // committed. Defense-in-depth until the propose-path drop
+                // site is traced and fixed.
+                if all.len() < total {
+                    return Err(PgWireError::UserError(Box::new(ErrorInfo::new(
+                        "ERROR".to_owned(),
+                        "XX000".to_owned(),
+                        format!(
+                            "incomplete batch: {}/{} statements produced responses — \
+                             some work may have been dropped; retry with a smaller batch",
+                            all.len(),
+                            total,
+                        ),
+                    ))));
+                }
                 Ok(all)
             }
         }