Fix draggable Attribute Rendering for Blazor Elements

[BrundhaVelusamy]

Description

This change fixes rendering of the HTML draggable attribute in Blazor.

Previously, when a bool value was supplied to an element attribute such as:

<div draggable="@isDraggable">

Blazor treated draggable as a standard HTML boolean attribute. As a result, it rendered a bare draggable attribute when the value was true and omitted the attribute entirely when the value was false. Since draggable is an enumerated attribute rather than a boolean attribute, this produced invalid HTML and could lead to inconsistent drag-and-drop behavior in browsers.

This update changes the rendering behavior so that:

• element attributes named draggable (case-insensitive) are treated specially
• true is rendered as draggable="true"
• false is rendered as draggable="false"
• the change applies only to element attributes and does not affect component parameters
• component parameters continue to receive boxed bool values, preserving existing [Parameter] bool behavior
• existing SSR, render batch serialization, and interactive rendering paths continue to work without modification since they already support string-valued attribute frames

This ensures that Blazor emits spec-compliant HTML for the draggable attribute and provides consistent drag-and-drop behavior across browsers.

Output

Before:

DraggableAttr_Issue.mp4

After:

DraggableAttr_Fix.mp4

Fixes #60137

[dotnet-policy-service]

Thanks for your PR, @BrundhaVelusamy. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.