Add debug_level stub to mock options object

The HTTPX::ErrorResponse constructor also calls options.debug_level
during error logging. Add this stub to prevent the test from failing with:

  received unexpected message :debug_level with (no args)

🤖 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

@@ -247,7 +247,7 @@
               yielder.call("#{original_chunks[0]}\n")
               # Simulate connection error mid-stream by creating a mock error response
               # Create a minimal mock request object that satisfies the ErrorResponse constructor
-              mock_options = instance_double(HTTPX::Options, timeout: {})
+              mock_options = instance_double(HTTPX::Options, timeout: {}, debug_level: 0)
               mock_request = instance_double(
                 HTTPX::Request,
                 uri: URI(render_full_url),