Fix HTTPError initialization in integration test

The HTTPX::HTTPError constructor expects a single response object argument,
not two separate arguments. Updated the test to properly create an
ErrorResponse object and pass it to HTTPError.

This fixes the test failure:
  ArgumentError: wrong number of arguments (given 2, expected 1)

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

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

Author: justin808

react_on_rails_pro/spec/react_on_rails_pro/request_spec.rb

@@ -246,7 +246,12 @@
             mock_streaming_response(render_full_url, 200) do |yielder|
               yielder.call("#{original_chunks[0]}\n")
               # Simulate connection error mid-stream
-              raise HTTPX::HTTPError.new("Connection error", nil)
+              # HTTPError expects a response object, so create a mock error response
+              error_response = HTTPX::ErrorResponse.new(
+                HTTPX::Request.new("POST", render_full_url),
+                StandardError.new("Connection closed")
+              )
+              raise HTTPX::HTTPError, error_response
             end
           else
             # Second attempt: complete all chunks successfully