Replace gpt4o-mini with deepseek

src/AI.hs

@@ -47,7 +47,7 @@ completions c prompt = checkpointCallStack $ do
   let opts = defaults & header "Authorization" .~ ["Bearer " <> c ^. openrouterKey . re utf8]
   let j =
         object
-          [ "model" .= ("openai/gpt-4o-mini" :: Text),
+          [ "model" .= ("~deepseek/deepseek-flash-latest" :: Text),
             "messages"
               .= [object ["role" .= ("user" :: Text), "content" .= prompt]]
           ]