🌐 feat: OpenRouter Web Search (#9853)

* 🌐 feat: OpenRouter Web Search

- Added tests for handling web_search parameter with OpenRouter in various scenarios.
- Implemented logic to manage web_search in modelOptions and addParams/dropParams.
- Ensured correct configuration of llmConfig and modelKwargs for OpenRouter, including handling of plugins.
- Improved overall integration of OpenRouter with OpenAI API, ensuring expected behavior across different configurations.

* chore: bump @librechat/agents to v2.4.81

packages/api/src/endpoints/openai/llm.ts

@@ -180,7 +180,12 @@ export function getOpenAILLMConfig({
     enableWebSearch = false;
   }
 
-  if (enableWebSearch) {
+  if (useOpenRouter && enableWebSearch) {
+    /** OpenRouter expects web search as a plugins parameter */
+    modelKwargs.plugins = [{ id: 'web' }];
+    hasModelKwargs = true;
+  } else if (enableWebSearch) {
+    /** Standard OpenAI web search uses tools API */
     llmConfig.useResponsesApi = true;
     tools.push({ type: 'web_search_preview' });
   }