[8.x] [obs AI Assistant] fix title_conversation failing test (elastic#216112) (elastic#216511)

# Backport

This will backport the following commits from `main` to `8.x`:
- [[obs AI Assistant] fix title_conversation failing test
(elastic#216112)](elastic#216112)

<!--- Backport version: 9.6.6 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

<!--BACKPORT [{"author":{"name":"Arturo
Lidueña","email":"[email protected]"},"sourceCommit":{"committedDate":"2025-03-31T14:56:32Z","message":"[obs
AI Assistant] fix title_conversation failing test (elastic#216112)\n\nCloses
elastic#215952\n\n[obs AI Assistant] fix title_conversation failing
test","sha":"3c9593b1a62aaa34922f27b2689699f2e545f37f","branchLabelMapping":{"^v9.1.0$":"main","^v8.19.0$":"8.x","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["release_note:skip","Team:Obs
AI Assistant","backport:version","v9.1.0","v8.19.0"],"title":"[obs AI
Assistant] fix title_conversation failing
test","number":216112,"url":"https://github.com/elastic/kibana/pull/216112","mergeCommit":{"message":"[obs
AI Assistant] fix title_conversation failing test (elastic#216112)\n\nCloses
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AI Assistant] fix title_conversation failing test (elastic#216112)\n\nCloses
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BACKPORT-->

Author: arturoliduena

x-pack/test/api_integration/deployment_agnostic/apis/observability/ai_assistant/complete/functions/title_conversation.spec.ts

@@ -11,19 +11,20 @@ import {
   TITLE_CONVERSATION_FUNCTION_NAME,
   TITLE_SYSTEM_MESSAGE,
 } from '@kbn/observability-ai-assistant-plugin/server/service/client/operators/get_generated_title';
+import { MessageRole } from '@kbn/observability-ai-assistant-plugin/common';
 import {
   LlmProxy,
   createLlmProxy,
 } from '../../../../../../../observability_ai_assistant_api_integration/common/create_llm_proxy';
-import { chatComplete } from '../../utils/conversation';
+import { chatComplete, clearConversations } from '../../utils/conversation';
 import type { DeploymentAgnosticFtrProviderContext } from '../../../../../ftr_provider_context';
 
 export default function ApiTest({ getService }: DeploymentAgnosticFtrProviderContext) {
   const log = getService('log');
   const observabilityAIAssistantAPIClient = getService('observabilityAIAssistantApi');
+  const es = getService('es');
 
-  // Failing: See https://github.com/elastic/kibana/issues/215952
-  describe.skip('when calling the title_conversation function', function () {
+  describe('when calling the title_conversation function', function () {
     // Fails on MKI: https://github.com/elastic/kibana/issues/205581
     this.tags(['failsOnMKI']);
     let llmProxy: LlmProxy;
@@ -51,7 +52,8 @@ export default function ApiTest({ getService }: DeploymentAgnosticFtrProviderCon
       let conversationId: string;
 
       before(async () => {
-        void llmProxy.interceptTitle(TITLE);
+        await clearConversations(es);
+        const simulatorPromise = llmProxy.interceptTitle(TITLE);
         void llmProxy.interceptConversation('The sky is blue because of Rayleigh scattering.');
 
         const res = await chatComplete({
@@ -64,7 +66,12 @@ export default function ApiTest({ getService }: DeploymentAgnosticFtrProviderCon
 
         await llmProxy.waitForAllInterceptorsToHaveBeenCalled();
 
-        titleRequestBody = llmProxy.interceptedRequests[0].requestBody;
+        const simulator = await simulatorPromise;
+        titleRequestBody = simulator.requestBody;
+      });
+
+      after(async () => {
+        await clearConversations(es);
       });
 
       it('makes 2 requests to the LLM', () => {
@@ -73,13 +80,13 @@ export default function ApiTest({ getService }: DeploymentAgnosticFtrProviderCon
 
       it('sends the correct system message to the LLM for the title', () => {
         expect(
-          titleRequestBody.messages.find((message) => message.role === 'system')?.content
+          titleRequestBody.messages.find((message) => message.role === MessageRole.System)?.content
         ).to.be(TITLE_SYSTEM_MESSAGE);
       });
 
       it('sends the correct user message to the LLM for the title', () => {
         expect(
-          titleRequestBody.messages.find((message) => message.role === 'user')?.content
+          titleRequestBody.messages.find((message) => message.role === MessageRole.User)?.content
         ).to.contain('Why the sky is blue?');
       });