Add opt-in Timeout to PurgeInstancesFilter for partial purge

src/Client/Core/PurgeInstancesFilter.cs

@@ -14,4 +14,12 @@
     DateTimeOffset? CreatedTo = null,
     IEnumerable<OrchestrationRuntimeStatus>? Statuses = null)
 {
+    /// <summary>
+    /// Gets or sets the maximum amount of time to spend purging instances in a single call.
+    /// If <c>null</c> (default), all matching instances are purged with no time limit.
+    /// When set, the purge stops accepting new instances after this duration elapses
+    /// and returns with <see cref="PurgeResult.IsComplete"/> set to <c>false</c>.
+    /// Already-started instance deletions will complete before the method returns.
+    /// </summary>
+    public TimeSpan? Timeout { get; init; }
 }

src/Client/Grpc/GrpcDurableTaskClient.cs

@@ -488,6 +488,11 @@ public override Task<PurgeResult> PurgeAllInstancesAsync(
             request.PurgeInstanceFilter.RuntimeStatus.AddRange(filter.Statuses.Select(x => x.ToGrpcStatus()));
         }
 
+        if (filter?.Timeout is not null)
+        {
+            request.PurgeInstanceFilter.Timeout = Google.Protobuf.WellKnownTypes.Duration.FromTimeSpan(filter.Timeout.Value);
+        }
+
         return this.PurgeInstancesCoreAsync(request, cancellation);
     }
 

src/Grpc/orchestrator_service.proto

@@ -517,6 +517,7 @@ message PurgeInstanceFilter {
     google.protobuf.Timestamp createdTimeFrom = 1;
     google.protobuf.Timestamp createdTimeTo = 2;
     repeated OrchestrationStatus runtimeStatus = 3;
+    google.protobuf.Duration timeout = 4;
 }
 
 message PurgeInstancesResponse {