Address code review: replace wildcard imports, use fixed timestamps in tests

Agent-Logs-Url: https://github.com/microsoft/durabletask-java/sessions/c4d58a2b-9982-49e3-bc9d-0b8527119032

Co-authored-by: bachuv <15795068+bachuv@users.noreply.github.com>

Author: Copilot

client/src/test/java/com/microsoft/durabletask/DurableTaskGrpcClientTest.java

@@ -3,7 +3,28 @@
 
 package com.microsoft.durabletask;
 
-import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.*;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.CreateInstanceRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.CreateInstanceResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.CreateTaskHubRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.CreateTaskHubResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.DeleteTaskHubRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.DeleteTaskHubResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.GetInstanceRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.GetInstanceResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.PurgeInstancesRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.PurgeInstancesResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.QueryInstancesRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.QueryInstancesResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.RaiseEventRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.RaiseEventResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.ResumeRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.ResumeResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.RewindInstanceRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.RewindInstanceResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.SuspendRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.SuspendResponse;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.TerminateRequest;
+import com.microsoft.durabletask.implementation.protobuf.OrchestratorService.TerminateResponse;
 import com.microsoft.durabletask.implementation.protobuf.TaskHubSidecarServiceGrpc;
 
 import io.grpc.*;
@@ -296,7 +317,7 @@ public void purgeInstances(PurgeInstancesRequest request, StreamObserver<PurgeIn
         });
 
         PurgeInstanceCriteria criteria = new PurgeInstanceCriteria()
-                .setCreatedTimeFrom(Instant.now().minus(Duration.ofDays(1)));
+                .setCreatedTimeFrom(Instant.parse("2026-01-01T00:00:00Z"));
 
         TimeoutException ex = assertThrows(TimeoutException.class, () ->
                 client.purgeInstances(criteria));
@@ -353,7 +374,7 @@ public void purgeInstances(PurgeInstancesRequest request, StreamObserver<PurgeIn
         });
 
         PurgeInstanceCriteria criteria = new PurgeInstanceCriteria()
-                .setCreatedTimeFrom(Instant.now().minus(Duration.ofDays(1)));
+                .setCreatedTimeFrom(Instant.parse("2026-01-01T00:00:00Z"));
 
         NoSuchElementException ex = assertThrows(NoSuchElementException.class, () ->
                 client.purgeInstances(criteria));