Add explicit TimeoutException rethrow in waitForInstanceStart, waitForInstanceCompletion, purgeInstances

Update rethrow logic after toException translation to check TimeoutException
first, then RuntimeException, with defensive fallback as last resort.

Agent-Logs-Url: https://github.com/microsoft/durabletask-java/sessions/2852d301-7a07-419c-a4f5-036184610079

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

Author: Copilot

client/src/main/java/com/microsoft/durabletask/DurableTaskGrpcClient.java

@@ -227,7 +227,9 @@ public OrchestrationMetadata waitForInstanceStart(String instanceId, Duration ti
                 throw new TimeoutException("Start orchestration timeout reached.");
             }
             Exception translated = StatusRuntimeExceptionHelper.toException(e, "waitForInstanceStart");
-            if (translated instanceof RuntimeException) {
+            if (translated instanceof TimeoutException) {
+                throw (TimeoutException) translated;
+            } else if (translated instanceof RuntimeException) {
                 throw (RuntimeException) translated;
             }
             throw new RuntimeException(translated);
@@ -258,7 +260,9 @@ public OrchestrationMetadata waitForInstanceCompletion(String instanceId, Durati
                 throw new TimeoutException("Orchestration instance completion timeout reached.");
             }
             Exception translated = StatusRuntimeExceptionHelper.toException(e, "waitForInstanceCompletion");
-            if (translated instanceof RuntimeException) {
+            if (translated instanceof TimeoutException) {
+                throw (TimeoutException) translated;
+            } else if (translated instanceof RuntimeException) {
                 throw (RuntimeException) translated;
             }
             throw new RuntimeException(translated);
@@ -370,7 +374,9 @@ public PurgeResult purgeInstances(PurgeInstanceCriteria purgeInstanceCriteria) t
                 throw new TimeoutException(timeOutException);
             }
             Exception translated = StatusRuntimeExceptionHelper.toException(e, "purgeInstances");
-            if (translated instanceof RuntimeException) {
+            if (translated instanceof TimeoutException) {
+                throw (TimeoutException) translated;
+            } else if (translated instanceof RuntimeException) {
                 throw (RuntimeException) translated;
             }
             throw new RuntimeException(translated);