[Broken Build]: Attempting upgrade to .Net 10 Preview 1 results in missing virtual directory '_framework' content

[MarkStega]

Issue Description

I have a project composed of three csproj projects in a single .sln file

The layout is:

Components -- sdk is "Microsoft.NET.Sdk.Razor"; contains a number of Blazor components
Website -- sdk is "Microsoft.NET.Sdk.Razor"; contains a number of pages each with components from Components and app.razor
Server -- sdk is "Microsoft.NET.Sdk.Web"; contains a very straight forward Web server that hosts the Blazor app with server rendering.

Components is .Net 8, Website & Server are .Net 9 based and everything works.

I attempted to move to .Net 10-P1 by changing the target framework and updating the nuget references in Website & Website.Server

Everything builds but when the website spins up (using F5 in Visual Studio) the load of '<script src="_framework/blazor.server.js"></script>' fails with a 404 error.

Steps to Reproduce

See supplied minimal repo project referenced in the succeeding comment

Expected Behavior

Able to upgrade form .Net 9 to .Net 10 P1

Actual Behavior

Non runnable website after the upgrade

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2025-03-05: Removed request for guidance now that a minimal reproduction project is available.

[MarkStega]

I have created a minimal project reproduction of the error.

The public repository is https://github.com/materia-technologies-inc/DN9To10.git

If you checkout the commit 'DN9 working demonstration project', build, run, you will see a minimal component being displayed.

Checking out the next commit 'DN10 demonstration of bad '_framework' generation', build, run, you will see the failure to load blazor.server.js

The only differences between the two commits is the content of website.csproj & website.server.csproj going from .net 9 to .net 10