Current limitation: The Diagram component does not provide native context menu integration. There are no events like OnShapeContextMenu or OnConnectionContextMenu that fire on right-click. Developers cannot show contextual actions (edit, delete, copy, connect) when user right-clicks on diagram elements.

Requested feature: Add context menu support for Diagram elements:

1. Context menu events:
   • OnShapeContextMenu — fires on right-click on a shape
   • OnConnectionContextMenu — fires on right-click on a connection
   • OnCanvasContextMenu — fires on right-click on empty canvas area (for "paste", "add shape" actions)
2. Event arguments:
   • DiagramShapeContextMenuEventArgs:
     • ShapeId — the clicked shape identifier
     • ClientX, ClientY — mouse position for menu placement
     • PageX, PageY — page coordinates
   • DiagramConnectionContextMenuEventArgs:
     • ConnectionId — the clicked connection identifier
     • FromShapeId, ToShapeId — connected shape identifiers
     • ClientX, ClientY, PageX, PageY
   • DiagramCanvasContextMenuEventArgs:
     • ClientX, ClientY, PageX, PageY
     • DiagramX, DiagramY — coordinates in diagram space (for placing new shapes)
3. Integration with TelerikContextMenu:
   • Ability to bind TelerikContextMenu to diagram and show it on right-click events
   • Automatic prevention of browser default context menu

Use case:
In workflow/process diagram editors, context menu is essential for:

• Shape actions: Edit, Delete, Duplicate, Copy/Paste, Change type, View details
• Connection actions: Edit transition, Delete, Change routing
• Canvas actions: Paste, Add new shape at cursor position, Zoom controls
• Conditional actions: Show different menu items based on shape type or state

Currently, there is no way to detect right-click on specific diagram elements. The only workaround is complex JavaScript interop to attach event listeners to SVG elements, which is fragile and breaks on re-render.

Example of desired API:

<TelerikDiagram @ref="@DiagramRef"
                OnShapeContextMenu="@OnShapeRightClick"
                OnConnectionContextMenu="@OnConnectionRightClick"
                OnCanvasContextMenu="@OnCanvasRightClick">
    <DiagramShapes>
        @foreach (var shape in Shapes)
        {
            <DiagramShape Id="@shape.Id">
                <DiagramShapeContent Text="@shape.Name" />
            </DiagramShape>
        }
    </DiagramShapes>
</TelerikDiagram>

<TelerikContextMenu @ref="@ShapeContextMenu" 
                    Data="@ShapeMenuItems"
                    OnClick="@OnShapeMenuClick">
    <ItemTemplate Context="item">
        <TelerikFontIcon Icon="@item.Icon" />
        <span>@item.Text</span>
    </ItemTemplate>
</TelerikContextMenu>

@code {
    private TelerikContextMenu<MenuItem>? ShapeContextMenu;
    private string? ClickedShapeId;
    
    private async Task OnShapeRightClick(DiagramShapeContextMenuEventArgs args)
    {
        ClickedShapeId = args.ShapeId;
        await ShapeContextMenu.ShowAsync(args.ClientX, args.ClientY);
    }
    
    private async Task OnShapeMenuClick(MenuItem item)
    {
        switch (item.Action)
        {
            case "edit":
                await OpenShapeEditor(ClickedShapeId);
                break;
            case "delete":
                await DeleteShape(ClickedShapeId);
                break;
            case "duplicate":
                await DuplicateShape(ClickedShapeId);
                break;
        }
    }
}