Error running command csdevkit.addExistingProject: Run into errors while reloading the solution: Error: Project name 'ConsoleApp1Ex' already exists in the 'Root' solution folder.

Describe the issue

1.Not a regression.
2.Low priority.

Error running command csdevkit.addExistingProject: Run into errors while reloading the solution: Error: Project name 'ConsoleApp1Ex' already exists in the 'Root' solution folder.. This is likely caused by the extension that contributes csdevkit.addExistingProject.

Collect logs

csdevkit-logs-2026-08-06T07-18-06.zip

Steps to reproduce

1.Create a Project1 (C# Console app) in the Folder1.
2.In C# project Details, right click the Folder1->Solution File Management->Add Existing Project->Add Project2, located in Folder2 under a different path.
3.When prompted in the image below, click Add Project to Workspace.

4.In C# project Details, right click the Folder1->Solution File Management->Remove Project->Remove this existing project2.
5.Repeat step2, add back the existing Project2 that was just removed and observe.

Expected behavior

This existing project can be added again.

Environment information

.NET Install Tool: Pre-release 3.1.0
C# Dev Kit Extension: Pre-release v3.29.195
C# Extension: Pre-release v2.148.23
.NET SDKs:  11.0.100-preview.6.26359.118
VSCode Stable: 1.132.0
Platform: Windows X64 

Start by reproducing the csdevkit.addExistingProject flow with the listed steps: add Project2, remove it, then add it again. Trace the solution file management handling around reload and confirm that the existing project can be added again without the duplicate 'ConsoleApp1Ex' error.