fix(client): signal completion for final SSE events

Signal normal completion before auto-closing streams for final events so cancellation cannot report a contradictory terminal outcome. Apply this to the shared listener and the v0.3 JSON-RPC listener.

This fixes #1170

Author: kabir

client/transport/spi/src/main/java/org/a2aproject/sdk/client/transport/spi/sse/AbstractSSEEventListener.java

@@ -118,6 +118,7 @@ protected void handleEvent(StreamingEventKind event, @Nullable Future<Void> futu
         // This covers late subscriptions to completed tasks and ensures no connection leaks
         if (shouldAutoClose(event) && future != null) {
             LOGGER.fine("Auto-closing SSE connection for final event: " + event.getClass().getSimpleName());
+            signalTerminal(null);
             future.cancel(true); // close SSE channel
         }
     }

compat-0.3/client/transport/jsonrpc/src/main/java/org/a2aproject/sdk/compat03/client/transport/jsonrpc/sse/SSEEventListener_v0_3.java

@@ -72,6 +72,7 @@ private void handleMessage(JsonObject jsonObject, Future<Void> future) throws Js
             StreamingEventKind_v0_3 event = JsonUtil_v0_3.fromJson(resultJson, StreamingEventKind_v0_3.class);
             eventHandler.accept(event);
             if (event instanceof TaskStatusUpdateEvent_v0_3 tsue && tsue.isFinal()) {
+                signalTerminal(null);
                 future.cancel(true); // close SSE channel
             }
         } else {