addressed PR feedback

Author: bachuv

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

@@ -240,8 +240,12 @@ public abstract OrchestrationMetadata waitForInstanceCompletion(
      *
      * @param query filter criteria: completion-time window, terminal runtime statuses, page size, and pagination cursor
      * @return a page of matching instance IDs and a cursor for the next page
+     * @throws UnsupportedOperationException if the current client implementation does not support listing instance IDs
      */
-    public abstract ListInstanceIdsResult listInstanceIds(ListInstanceIdsQuery query);
+    public ListInstanceIdsResult listInstanceIds(ListInstanceIdsQuery query) {
+        throw new UnsupportedOperationException(
+                "Listing instance IDs is not supported by this client implementation.");
+    }
 
     /**
      * Gets the full history of an orchestration instance as an ordered list of {@link HistoryEvent} objects.
@@ -251,8 +255,12 @@ public abstract OrchestrationMetadata waitForInstanceCompletion(
      *
      * @param instanceId the unique ID of the orchestration instance whose history to fetch
      * @return the instance's history events in order; empty if the instance has no history
+     * @throws UnsupportedOperationException if the current client implementation does not support history retrieval
      */
-    public abstract List<HistoryEvent> getOrchestrationHistory(String instanceId);
+    public List<HistoryEvent> getOrchestrationHistory(String instanceId) {
+        throw new UnsupportedOperationException(
+                "Retrieving orchestration history is not supported by this client implementation.");
+    }
 
     /**
      * Initializes the target task hub data store.

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

@@ -68,10 +68,14 @@ public ListInstanceIdsQuery setCompletedTimeTo(@Nullable Instant completedTimeTo
      * A page may contain fewer IDs than the page size even when more results exist; always use
      * {@link ListInstanceIdsResult#getContinuationToken()} to determine whether to continue paging.
      *
-     * @param pageSize the maximum number of instance IDs to return per page
+     * @param pageSize the maximum number of instance IDs to return per page; must be greater than zero
      * @return this query object
+     * @throws IllegalArgumentException if {@code pageSize} is less than 1
      */
     public ListInstanceIdsQuery setPageSize(int pageSize) {
+        if (pageSize < 1) {
+            throw new IllegalArgumentException("pageSize must be at least 1.");
+        }
         this.pageSize = pageSize;
         return this;
     }