fix(vertexai): correct URL construction for global endpoint

When location is set to 'global', the plugin was incorrectly constructing
the URL as https://global-aiplatform.googleapis.com, which results in 404.

The correct URL for global endpoint should be https://aiplatform.googleapis.com
without the location prefix.

This fix applies to:
- list-models.ts: Model listing endpoint
- upsert_datapoints.ts: Vector search datapoint upsert endpoint
- predict.ts: Prediction endpoint
- evaluation/evaluator_factory.ts: Evaluation service endpoint
- modelgarden/v2/llama.ts: Llama model garden endpoint

Implementation uses a ternary operator for optimal performance and follows
the same pattern as Google's official Gen AI SDK.

Fixes #3651

Author: yeonjaee

js/plugins/vertexai/src/evaluation/evaluator_factory.ts

@@ -82,7 +82,11 @@ export class EvaluatorFactory {
 
         metadata.input = request;
         const client = await this.auth.getClient();
-        const url = `https://${this.location}-aiplatform.googleapis.com/v1beta1/${locationName}:evaluateInstances`;
+        const baseUrl = this.location === 'global'
+          ? 'https://aiplatform.googleapis.com'
+          : `https://${this.location}-aiplatform.googleapis.com`;
+
+        const url = `${baseUrl}/v1beta1/${locationName}:evaluateInstances`;
         const response = await client.request({
           url,
           method: 'POST',

js/plugins/vertexai/src/list-models.ts

@@ -38,8 +38,14 @@ export async function listModels(
 ): Promise<Model[]> {
   const fetch = (await import('node-fetch')).default;
   const accessToken = await authClient.getAccessToken();
+  
+  // Global endpoint uses base URL without location prefix
+  const baseUrl = location === 'global'
+    ? 'https://aiplatform.googleapis.com'
+    : `https://${location}-aiplatform.googleapis.com`;
+  
   const response = await fetch(
-    `https://${location}-aiplatform.googleapis.com/v1beta1/publishers/google/models`,
+    `${baseUrl}/v1beta1/publishers/google/models`,
     {
       method: 'GET',
       headers: {

js/plugins/vertexai/src/modelgarden/v2/llama.ts

@@ -146,10 +146,13 @@ async function resolveOptions(
   clientOptions: ClientOptions,
   requestConfig?: LlamaConfig
 ) {
-  const baseUrlTemplate =
-    clientOptions.baseUrlTemplate ??
-    'https://{location}-aiplatform.googleapis.com/v1/projects/{projectId}/locations/{location}/endpoints/openapi';
   const location = requestConfig?.location || clientOptions.location;
+  const defaultTemplate = location === 'global'
+    ? 'https://aiplatform.googleapis.com/v1/projects/{projectId}/locations/{location}/endpoints/openapi'
+    : 'https://{location}-aiplatform.googleapis.com/v1/projects/{projectId}/locations/{location}/endpoints/openapi';
+
+  const baseUrlTemplate = clientOptions.baseUrlTemplate ?? defaultTemplate;
+
   const baseURL = baseUrlTemplate
     .replace(/{location}/g, location)
     .replace(/{projectId}/g, clientOptions.projectId);

js/plugins/vertexai/src/predict.ts

@@ -23,8 +23,11 @@ function endpoint(options: {
   location: string;
   model: string;
 }) {
+  const baseUrl = options.location === 'global'
+    ? 'https://aiplatform.googleapis.com'
+    : `https://${options.location}-aiplatform.googleapis.com`;
   return (
-    `https://${options.location}-aiplatform.googleapis.com/v1/` +
+    `${baseUrl}/v1/` +
     `projects/${options.projectId}/locations/${options.location}/` +
     `publishers/google/models/${options.model}:predict`
   );

js/plugins/vertexai/src/vectorsearch/vector_search/upsert_datapoints.ts

@@ -45,7 +45,11 @@ export async function upsertDatapoints(
 ): Promise<void> {
   const { datapoints, authClient, projectId, location, indexId } = params;
   const accessToken = await authClient.getAccessToken();
-  const url = `https://${location}-aiplatform.googleapis.com/v1/projects/${projectId}/locations/${location}/indexes/${indexId}:upsertDatapoints`;
+  const baseUrl = location === 'global'
+    ? 'https://aiplatform.googleapis.com'
+    : `https://${location}-aiplatform.googleapis.com`;
+
+  const url = `${baseUrl}/v1/projects/${projectId}/locations/${location}/indexes/${indexId}:upsertDatapoints`;
 
   const requestBody = {
     datapoints: datapoints.map((dp) => {