Beginner UX: guided endpoint connection header (#11228)

Validated on the combined batch board + this branch: i18n suites 16/16 with Vietnamese translations of the new endpoint strings added here. Guided connection header with the /v1 URL and test action leads; advanced protocols demoted. Thank you @ignamiranda!

src/app/(dashboard)/dashboard/endpoint/EndpointPageClient.tsx

@@ -2360,7 +2360,19 @@ function ProviderModelsModal({
         <div className="flex flex-col gap-1">
           {groupModels.map((m) => {
             const copyKey = `modal-${m.id}`;
-            return (
+  return (
+    <div className="flex flex-col gap-4">
+      <div className="flex flex-col gap-2 mb-2">
+        <h1 className="text-2xl font-bold">{t("endpoint.title")}</h1>
+        <p className="text-text-muted">{t("endpoint.subtitle")}</p>
+        <div className="flex items-center gap-3 mt-2">
+          <code className="text-sm bg-card-subtle px-3 py-1 rounded-md text-text-main font-mono">{useDisplayBaseUrl()}/v1</code>
+          <a href="#test" className="text-sm text-action font-medium hover:underline">{t("endpoint.testEndpoint")}</a>
+        </div>
+      </div>
+      <div className="flex items-center gap-2 text-xs text-text-muted">
+        <span>{t("endpoint.advancedProtocols")}</span>
+      </div>
               <div
                 key={m.id}
                 className="flex items-center gap-2 px-3 py-2 rounded-lg hover:bg-surface/60 group"

src/i18n/messages/en.json

@@ -3844,6 +3844,9 @@
   },
   "endpoint": {
     "title": "API Endpoint",
+    "subtitle": "Use the OpenAI-compatible endpoint with most SDKs and tools.",
+    "testEndpoint": "Test endpoint →",
+    "advancedProtocols": "Advanced protocols",
     "available": "Available Endpoints",
     "cloudProxy": "Cloud Proxy",
     "disableConfirm": "Are you sure you want to disable cloud proxy?",

src/i18n/messages/vi.json

@@ -4151,7 +4151,10 @@
     "notionIntegrationHelp": "Tạo một Tích hợp nội bộ tại",
     "notionIntegrationToken": "Token tích hợp nội bộ Notion",
     "notionNotConnected": "Chưa kết nối",
-    "notionTokenConfigured": "Đã cấu hình token. Các công cụ Notion khả dụng qua MCP."
+    "notionTokenConfigured": "Đã cấu hình token. Các công cụ Notion khả dụng qua MCP.",
+    "subtitle": "Dùng endpoint tương thích OpenAI với hầu hết SDK và công cụ.",
+    "testEndpoint": "Kiểm tra endpoint →",
+    "advancedProtocols": "Giao thức nâng cao"
   },
   "endpoints": {
     "tabProxy": "Endpoint Proxy",