Address review feedback: add missing require, fix redundant test

- Add explicit require for check/result in client_stub.rb so the file
  is standalone-loadable
- Rename test_accepts_string_keys to test_accepts_symbol_keys and
  actually pass symbol keys to provide distinct coverage

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: rosa

lib/rspamd/client_stub.rb

@@ -1,3 +1,5 @@
+require "rspamd/check/result"
+
 module Rspamd
   class ClientStub
     HAM_RESULT = Check::Result.new(

test/rails_test.rb

@@ -48,8 +48,8 @@ def test_reset_clears_config_and_clients
     assert_instance_of Rspamd::ClientStub, client
   end
 
-  def test_accepts_string_keys
-    Rspamd::Rails.setup("enabled" => true, "outbound" => { "host" => "localhost", "port" => 11334 })
+  def test_accepts_symbol_keys
+    Rspamd::Rails.setup(enabled: true, outbound: { host: "localhost", port: 11334 })
 
     client = Rspamd::Rails.client_for(:outbound)
     assert_instance_of Rspamd::Client, client