Use mock request object instead of real HTTPX::Request

The HTTPX::Request constructor requires 3-4 arguments, not 2. Instead of
figuring out the exact signature, use an RSpec instance_double to create
a minimal mock request object that satisfies the ErrorResponse constructor.

This fixes the test failure:
  ArgumentError: wrong number of arguments (given 2, expected 3..4)

🤖 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

@@ -245,10 +245,11 @@
             # This simulates a connection error after partial data is sent
             mock_streaming_response(render_full_url, 200) do |yielder|
               yielder.call("#{original_chunks[0]}\n")
-              # Simulate connection error mid-stream
-              # HTTPError expects a response object, so create a mock error response
+              # Simulate connection error mid-stream by creating a mock error response
+              # Create a minimal mock request object that satisfies the ErrorResponse constructor
+              mock_request = instance_double(HTTPX::Request, uri: URI(render_full_url))
               error_response = HTTPX::ErrorResponse.new(
-                HTTPX::Request.new("POST", render_full_url),
+                mock_request,
                 StandardError.new("Connection closed")
               )
               raise HTTPX::HTTPError, error_response