[Search] Serverless hide AI assistant from side nav for viewer (elastic#246966)

## Summary

Currently in the Serverless search solution and when chatExperience set
to `classic`, the viewer user is redirected to classic nav home page
when tried to visit AI assistant app.
In this PR,

- [ ] updated to hide AI assistant from side nav for serveless search
and observability.
- [ ] modified redirect default route to serverless search home page



https://github.com/user-attachments/assets/e7af8d8d-cb59-4ede-932d-157741fa3d3d

How to test:
Manually set chatExperience to `classic`. 
```
POST kbn://internal/kibana/settings
{
  "changes": {
    "aiAssistant:preferredChatExperience": "agent"
  }
}
```
Tests completed:

- [ ] Confirmed self managed behaviour remains unchanged. Which is -
classic nav AI assistant app is hidden for user with less privilege.
- [ ] Confirmed self managed security and observability solution nav
works as expected.


### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Viduni Wickramarachchi <viduni.ushanka@gmail.com>

Author: 3 people

x-pack/platform/plugins/private/observability_ai_assistant_management/public/app.tsx

@@ -48,7 +48,7 @@ export const mountManagementSection = async ({ core, mountParams, config }: Moun
 
   ReactDOM.render(
     wrapWithTheme(
-      <RedirectToHomeIfUnauthorized coreStart={coreStart}>
+      <RedirectToHomeIfUnauthorized coreStart={coreStart} cloud={startDeps?.cloud}>
         <I18nProvider>
           <KibanaContextProvider services={{ ...coreStart, ...startDeps }}>
             <AppContextProvider value={{ setBreadcrumbs, config }}>

x-pack/platform/plugins/private/observability_ai_assistant_management/public/helpers/test_helper.tsx

@@ -17,6 +17,7 @@ import { RouterProvider } from '@kbn/typed-react-router-config';
 import { KibanaContextProvider } from '@kbn/kibana-react-plugin/public';
 import { merge } from 'lodash';
 import type { DeepPartial } from 'utility-types';
+import { cloudMock } from '@kbn/cloud-plugin/public/mocks';
 import type { AppContextValue } from '../context/app_context';
 import { AppContextProvider } from '../context/app_context';
 import { RedirectToHomeIfUnauthorized } from '../routes/components/redirect_to_home_if_unauthorized';
@@ -25,6 +26,7 @@ import type { CoreStartWithStartDeps } from '../hooks/use_kibana';
 
 export const coreStartMock = coreMock.createStart();
 
+export const cloudStartMock = cloudMock.createStart();
 const queryClient = new QueryClient({
   defaultOptions: {
     queries: {
@@ -80,7 +82,7 @@ export const render = (
   const TestWrapper = ({ children }: { children: React.ReactNode }) => (
     // @ts-ignore
     <IntlProvider locale="en-US">
-      <RedirectToHomeIfUnauthorized coreStart={mergedCoreStartMock}>
+      <RedirectToHomeIfUnauthorized coreStart={mergedCoreStartMock} cloud={cloudStartMock}>
         <KibanaContextProvider services={{ ...mergedCoreStartMock, ...startDeps }}>
           <AppContextProvider value={appContextValue}>
             <QueryClientProvider client={queryClient}>

x-pack/platform/plugins/private/observability_ai_assistant_management/public/plugin.test.ts

@@ -54,8 +54,11 @@ describe('Observability AI Assistant Management plugin', () => {
     } as any);
 
   describe('Licensing', () => {
-    it('is disabled by default, enabled only for enterprise, and disabled for platinum', async () => {
-      const plugin = new AiAssistantManagementObservabilityPlugin({
+    let plugin: any;
+    let management: ManagementSetup;
+    let coreSetup: CoreSetup<any, any>;
+    beforeEach(async () => {
+      plugin = new AiAssistantManagementObservabilityPlugin({
         config: {
           get: jest.fn(() => ({
             logSourcesEnabled: true,
@@ -64,23 +67,31 @@ describe('Observability AI Assistant Management plugin', () => {
         },
         env: { packageInfo: { buildFlavor: 'traditional', branch: 'main' } },
       } as unknown as PluginInitializerContext);
-
-      const management = createManagementMock();
-      const coreSetup = createCoreSetupMock();
-
+      management = createManagementMock();
+      coreSetup = createCoreSetupMock();
       await plugin.setup(coreSetup, {
         management,
         observabilityAIAssistant: {} as any,
         ml: {} as any,
       });
+    });
+    afterEach(() => {
+      plugin.stop();
+    });
 
+    it('is disabled by default, enabled for enterprise if the AI Assistant is enabled, and disabled for platinum', () => {
       const app = (management.sections.section.ai as any).getApps()[0];
       expect(app).toBeDefined();
       expect(app.enabled).toBe(false);
 
       // Start with platinum
       const license$ = new BehaviorSubject<any>(makeLicense('platinum'));
-      plugin.start({} as CoreStart, { licensing: { license$ } } as any);
+      plugin.start(
+        {
+          application: { capabilities: { observabilityAIAssistant: { show: true } } },
+        } as unknown as CoreStart,
+        { licensing: { license$ } } as any
+      );
       expect(app.enabled).toBe(false);
 
       // Switch to enterprise
@@ -95,5 +106,33 @@ describe('Observability AI Assistant Management plugin', () => {
       license$.next(makeLicense('basic'));
       expect(app.enabled).toBe(false);
     });
+
+    it('is disabled by default for all license types when the AI Assistant is disabled', () => {
+      const app = (management.sections.section.ai as any).getApps()[0];
+      expect(app).toBeDefined();
+      expect(app.enabled).toBe(false);
+
+      // Start with platinum
+      const license$ = new BehaviorSubject<any>(makeLicense('platinum'));
+      plugin.start(
+        {
+          application: { capabilities: { observabilityAIAssistant: { show: false } } },
+        } as unknown as CoreStart,
+        { licensing: { license$ } } as any
+      );
+      expect(app.enabled).toBe(false);
+
+      // Switch to enterprise
+      license$.next(makeLicense('enterprise'));
+      expect(app.enabled).toBe(false);
+
+      // Switch to gold
+      license$.next(makeLicense('gold'));
+      expect(app.enabled).toBe(false);
+
+      // Switch to basic
+      license$.next(makeLicense('basic'));
+      expect(app.enabled).toBe(false);
+    });
   });
 });

x-pack/platform/plugins/private/observability_ai_assistant_management/public/plugin.ts

@@ -122,8 +122,9 @@ export class AiAssistantManagementObservabilityPlugin
     if (licensing) {
       this.licensingSubscription = licensing.license$.subscribe((license) => {
         const isEnterprise = license?.hasAtLeast('enterprise');
-
-        if (isEnterprise) {
+        const isAiAssistantEnabled =
+          coreStart.application.capabilities.observabilityAIAssistant?.show;
+        if (isEnterprise && isAiAssistantEnabled) {
           this.registeredApp?.enable();
         } else {
           this.registeredApp?.disable();

x-pack/platform/plugins/private/observability_ai_assistant_management/public/routes/components/redirect_to_home_if_unauthorized.tsx

@@ -12,12 +12,15 @@ import type { CoreStart } from '@kbn/core/public';
 import { AIChatExperience } from '@kbn/ai-assistant-common';
 import { AI_CHAT_EXPERIENCE_TYPE } from '@kbn/management-settings-ids';
 import { aiAssistantCapabilities } from '@kbn/observability-ai-assistant-plugin/public';
+import type { CloudStart } from '@kbn/cloud-plugin/public';
 
 export function RedirectToHomeIfUnauthorized({
   coreStart,
+  cloud,
   children,
 }: {
   coreStart: CoreStart;
+  cloud?: CloudStart;
   children: ReactNode;
 }) {
   const {
@@ -30,16 +33,22 @@ export function RedirectToHomeIfUnauthorized({
     [settings.client]
   );
   const chatExperience = useObservable(chatExperience$, AIChatExperience.Classic);
+  const isServerlessSearchSolution =
+    cloud?.isServerlessEnabled && cloud?.serverless?.projectType === 'search';
 
   const allowed =
     (capabilities?.observabilityAIAssistant?.[aiAssistantCapabilities.show] ?? false) &&
     chatExperience !== AIChatExperience.Agent;
 
   useEffect(() => {
     if (!allowed) {
-      navigateToApp('home');
+      if (isServerlessSearchSolution) {
+        navigateToApp('searchHomepage');
+      } else {
+        navigateToApp('home');
+      }
     }
-  }, [allowed, navigateToApp]);
+  }, [allowed, navigateToApp, isServerlessSearchSolution]);
 
   if (!allowed) return null;