fix(ui): improve agent debug and model test feedback

web/src/app/home/components/models-dialog/ModelsPanel.tsx

@@ -522,8 +522,9 @@ export default function ModelsPanel({
       setTestResult({ success: true, duration });
     } catch (err) {
       console.error('Failed to test model', err);
-      toast.error(t('models.testError') + ': ' + (err as CustomApiError).msg);
-      setTestResult(null);
+      const message = (err as CustomApiError).msg || t('models.testError');
+      toast.error(t('models.testError') + ': ' + message);
+      setTestResult({ success: false, message });
     } finally {
       setIsTesting(false);
     }

web/src/app/home/components/models-dialog/components/AddModelPopover.tsx

@@ -437,6 +437,14 @@ export default function AddModelPopover({
                       )}
                     </Button>
                   </div>
+                  {testResult?.success === false && (
+                    <p
+                      role="alert"
+                      className="rounded-md border border-destructive/30 bg-destructive/5 p-2 text-xs text-destructive [overflow-wrap:anywhere]"
+                    >
+                      {testResult.message}
+                    </p>
+                  )}
                 </div>
               </div>
             ) : (

web/src/app/home/components/models-dialog/components/ModelItem.tsx

@@ -412,6 +412,14 @@ export default function ModelItem({
               )}
             </Button>
           </div>
+          {testResult?.success === false && (
+            <p
+              role="alert"
+              className="rounded-md border border-destructive/30 bg-destructive/5 p-2 text-xs text-destructive [overflow-wrap:anywhere]"
+            >
+              {testResult.message}
+            </p>
+          )}
         </div>
       </PopoverContent>
     </Popover>

web/src/app/home/components/models-dialog/types.ts

@@ -27,10 +27,9 @@ export interface ProviderModels {
   rerank: RerankModel[];
 }
 
-export interface TestResult {
-  success: boolean;
-  duration: number;
-}
+export type TestResult =
+  | { success: true; duration: number }
+  | { success: false; message: string };
 
 export type SelectedScannedModel = {
   model: ScannedProviderModel;