PERF: Optimize .ai-debug-modal__tokens selector (#1390)

This is showing as the most expensive CSS selector in Discourse at the moment. Adding specific classes and dropping the general `span` selector will make this much cheaper.

Author: davidtaylorhq

assets/javascripts/discourse/components/modal/debug-ai-modal.gjs

@@ -144,11 +144,11 @@ export default class DebugAiModal extends Component {
             >{{i18n "discourse_ai.ai_bot.debug_ai_modal.response"}}</a></li>
         </ul>
         <div class="ai-debug-modal__tokens">
-          <span>
+          <span class="ai-debug-modal__tokens__count">
             {{i18n "discourse_ai.ai_bot.debug_ai_modal.request_tokens"}}
             {{this.info.request_tokens}}
           </span>
-          <span>
+          <span class="ai-debug-modal__tokens__count">
             {{i18n "discourse_ai.ai_bot.debug_ai_modal.response_tokens"}}
             {{this.info.response_tokens}}
           </span>

assets/stylesheets/modules/ai-bot/common/bot-replies.scss

@@ -139,7 +139,7 @@ span.onebox-ai-llm-title {
   }
 }
 
-.ai-debug-modal__tokens span {
+.ai-debug-modal__tokens__count {
   display: block;
 }