Wait for the sender before checking its status in NotificationServiceTest (#634)

Fixes #633.

Four tests in `NotificationServiceTest` (`basic_send_recv` and three
others with the same shape) wait only on the receiving workflow, then
assert that both workflows are SUCCESS. The receiver can finish as soon
as the sender's `send` step commits the message, which is before the
sender records SUCCESS. On a slow runner the sender was still PENDING,
as in the On Push run for #632, where the failure skipped that commit's
publish.

Each test now calls `handle2.getResult()` before the status asserts.
This is a test-only change. The other tests that assert a second handle
is SUCCESS (`DynamicQueuesTest`, `StaticQueuesTest`, `ForkTest`) already
wait on it first.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: devhawk

transact/src/test/java/dev/dbos/transact/notifications/NotificationServiceTest.java

@@ -187,6 +187,8 @@ public void basic_send_recv() throws Exception {
 
     String result = (String) handle1.getResult();
     assertEquals("HelloDBOS", result);
+    // The receiver can finish as soon as the send step commits, before the sender records SUCCESS.
+    handle2.getResult();
 
     assertEquals(WorkflowState.SUCCESS, handle1.getStatus().status());
     assertEquals(WorkflowState.SUCCESS, handle2.getStatus().status());
@@ -271,6 +273,8 @@ public void notopic() throws Exception {
 
     String result = (String) handle1.getResult();
     assertEquals("HelloDBOS", result);
+    // The receiver can finish as soon as the send step commits, before the sender records SUCCESS.
+    handle2.getResult();
 
     assertEquals(WorkflowState.SUCCESS, handle1.getStatus().status());
     assertEquals(WorkflowState.SUCCESS, handle2.getStatus().status());
@@ -333,6 +337,8 @@ public void sendNull() throws Exception {
 
     String result = (String) handle1.getResult();
     assertNull(result);
+    // The receiver can finish as soon as the send step commits, before the sender records SUCCESS.
+    handle2.getResult();
 
     assertEquals(WorkflowState.SUCCESS, handle1.getStatus().status());
     assertEquals(WorkflowState.SUCCESS, handle2.getStatus().status());
@@ -422,6 +428,8 @@ public void recvSleep() throws Exception {
 
     String result = (String) handle1.getResult();
     assertEquals("HelloDBOS", result);
+    // The receiver can finish as soon as the send step commits, before the sender records SUCCESS.
+    handle2.getResult();
 
     assertEquals(WorkflowState.SUCCESS, handle1.getStatus().status());
     assertEquals(WorkflowState.SUCCESS, handle2.getStatus().status());