Rename shutdown_worker_rejected to rejected_by_worker_shutdown

The old name was ambiguous — it could read as "the shutdown-worker
request was rejected." The new name clarifies that the poll was
rejected because of a worker shutdown.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: rkannan82

temporal/api/workflowservice/v1/request_response.proto

@@ -341,7 +341,7 @@ message PollWorkflowTaskQueueResponse {
     // When true, this empty response was caused by the server rejecting the poll
     // because the worker has been shut down via the ShutdownWorker API. The SDK
     // should stop polling on this task queue.
-    bool shutdown_worker_rejected = 17;
+    bool rejected_by_worker_shutdown = 17;
 }
 
 message RespondWorkflowTaskCompletedRequest {
@@ -543,7 +543,7 @@ message PollActivityTaskQueueResponse {
     // When true, this empty response was caused by the server rejecting the poll
     // because the worker has been shut down via the ShutdownWorker API. The SDK
     // should stop polling on this task queue.
-    bool shutdown_worker_rejected = 21;
+    bool rejected_by_worker_shutdown = 21;
 }
 
 message RecordActivityTaskHeartbeatRequest {
@@ -1934,7 +1934,7 @@ message PollNexusTaskQueueResponse {
     // When true, this empty response was caused by the server rejecting the poll
     // because the worker has been shut down via the ShutdownWorker API. The SDK
     // should stop polling on this task queue.
-    bool shutdown_worker_rejected = 4;
+    bool rejected_by_worker_shutdown = 4;
 }
 
 message RespondNexusTaskCompletedRequest {