Clear the per-request partial-result state after each query

The partial-result override and the warnings-supported flag live in
QueryContext's log4j thread-locals, but only QueryProfiling was being cleared
when a request finished. Transport threads are pooled, so a query that expressed
no preference inherited the previous query's override from the same thread: with
the cluster setting off and no request flag, an aggregation over a text/keyword
conflict intermittently returned a partial result (with a warning) instead of
failing -- observed 7 of 12 runs after an earlier request had set the flag.

Clear both flags alongside QueryProfiling in the response listener. Verified:
flag-absent requests now fail 12/12 when interleaved with explicit true
requests, while explicit true still returns the partial result.

Signed-off-by: Kai Huang <ahkcs@amazon.com>

Author: ahkcs

plugin/src/main/java/org/opensearch/sql/plugin/transport/TransportPPLQueryAction.java

@@ -385,7 +385,7 @@ public void onResponse(TransportPPLQueryResponse transportPPLQueryResponse) {
         try {
           delegate.onResponse(transportPPLQueryResponse);
         } finally {
-          QueryProfiling.clear();
+          clearRequestScopedState();
         }
       }
 
@@ -394,9 +394,21 @@ public void onFailure(Exception e) {
         try {
           delegate.onFailure(e);
         } finally {
-          QueryProfiling.clear();
+          clearRequestScopedState();
         }
       }
     };
   }
+
+  /**
+   * Clear the per-request state carried in {@link QueryContext}'s thread-locals. Transport threads
+   * are pooled, so anything left behind is inherited by the next query to run on this thread -- a
+   * request that expressed no partial-result preference would otherwise pick up the previous
+   * request's override.
+   */
+  private static void clearRequestScopedState() {
+    QueryProfiling.clear();
+    QueryContext.setPartialResultOverride(null);
+    QueryContext.setWarningsSupported(false);
+  }
 }