### Bug report

When the TreeList is set up for Popup editing, the "required" validation triggers immediately when the Popup form is opened.

### Reproduction of the problem

1) Create a Popup editable TreeList.

2) Add the DataAnnotation [Required] attribute to any of the Model properties.

3) Click the built-in "Add new record" command.

4) The editor of the required field is automatically focused and the validation triggers immediately.

The behavior can be observed in the TreeList Popup Editing demo: https://demos.telerik.com/aspnet-core/treelist/editing-popup

### Expected/desired behavior

The validation must trigger on blur, as in the jQuery demo.

### Environment

* **Telerik UI for ASP.NET Core version: 2025.2.520
* **Browser: [all]

Consider the use of TextWriter async methods for the HTML Helpers, for example the WriteInitializationScript methods.  In certain scenarios the use of the synchronous methods causes an exception: System.InvalidOperationException: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.

This can be resolved by explicitly enabling synchronous operations

services.Configure<IISServerOptions>(options =>
    {
        options.AllowSynchronousIO = true;
    });

though synchronous operations have been disabled by default at framework level as of .NET 3.0.

### Bug report

When dragging and dropping a file into a specified FileManager folder, the Upload request triggers twice.

### Reproduction of the problem

1. Open the FileManager Demo: https://demos.telerik.com/kendo-ui/filemanager/index

2. Open the browser's Network tab.

3. Drag and drop a file into the FileManager.

4. Two Upload requests are triggered one after another.

### Expected/desired behavior

When uploading a single file with drag & drop, a single Upload request must trigger. When using the default upload button to upload a file, a single request triggers as expected.

### Environment

* **Kendo UI version: 2024.4.1112
* **jQuery version: 3.7.1
* **Browser: [all]

Currently, the Content function for Steps in a Wizard only accepts a string value (see API here). 
This means that in order to add a partial view (bound to the current model and its properties), the most straightforward way I could find was to put the partial view (and any wrappers) in its own file and add an extension method "ToHtmlString()". For example:

@model MyModel

@(Html.Kendo().Wizard().Steps(step => {
    step.Add().Content(Html.Partial("~/Path/To/View/Wrapper.cshtml", Model).ToHtmlString());
})

using Microsoft.AspNetCore.Html;
using System.IO;

public static class HtmlContentExtensions
{
    public static string ToHtmlString(this IHtmlContent htmlContent)
    {
        if (htmlContent is HtmlString htmlString)
        {
            return htmlString.Value;
        }

        using StringWriter writer = new();
        htmlContent.WriteTo(writer, System.Text.Encodings.Web.HtmlEncoder.Default);
        return writer.ToString();
    }
}

@model MyModel

@(Html.Kendo().TabStrip().Items(tabstrip => {

    tabstrip.Add()
    .Content(@<div id="@Model.TabContainer" class="myTabWrapperClass"> 
       @await Html.PartialAsync("~/Path/To/View.cshtml", Model)
    </div>);

})