Add debug logging for client disconnects and improve error handling

Improvements:
- Add debug logging when client disconnects during streaming (producer/consumer)
- Remove unnecessary explicit nil return in rescue block
- Add test support for closed? method on mocked stream
- Only logs when logging_on_server is enabled

These changes improve observability for production debugging without
affecting normal operation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

react_on_rails_pro/lib/react_on_rails_pro/concerns/stream.rb

@@ -103,8 +103,9 @@ def build_producer_tasks(parent:, queue:)
             # Will be blocked if the queue is full until a chunk is dequeued
             queue.enqueue([idx, chunk])
           end
-        rescue IOError, Errno::EPIPE
+        rescue IOError, Errno::EPIPE => e
           # Client disconnected - stop producing
+          log_client_disconnect("producer", e)
           break
         end
       end
@@ -119,9 +120,17 @@ def build_writer_task(parent:, queue:)
           _idx_from_queue, item = pair
           response.stream.write(item)
         end
-      rescue IOError, Errno::EPIPE
+      rescue IOError, Errno::EPIPE => e
         # Client disconnected - stop writing
-        nil
+        log_client_disconnect("consumer", e)
+      end
+    end
+
+    def log_client_disconnect(context, exception)
+      return unless ReactOnRails.configuration.logging_on_server
+
+      ReactOnRails.configuration.logger.debug do
+        "[React on Rails Pro] Client disconnected during streaming (#{context}): #{exception.class}"
       end
     end
   end

react_on_rails_pro/spec/react_on_rails_pro/stream_spec.rb

@@ -388,6 +388,7 @@ def setup_stream_test(component_count: 2)
       allow(mocked_response).to receive(:stream).and_return(mocked_stream)
       allow(mocked_stream).to receive(:write)
       allow(mocked_stream).to receive(:close)
+      allow(mocked_stream).to receive(:closed?).and_return(false)
       allow(controller).to receive(:response).and_return(mocked_response)
 
       [component_queues, controller, mocked_stream]