[Roslyn] Tutorial misses information about netCore3.0 (unsupported!) is required to be installed to use the Roslyn .NET Standard Template and succeed with the tutorial

### Type of issue

Missing information

### Description

I attempted to create my first Roslyn Generator/Analyzer Project from scratch in VS2026 v18.0.2 using the linked tutorial guide, but just like the user here:
- https://github.com/dotnet/roslyn-sdk/issues/1131

*(which *should* be fixed from the issue state !!! )*

and latest updates and workloads provided from the Visual Studio Installer, I run into the same problems:

- We can not select to get a "real" `.NET Standard` Project, only be able to choose between different **.NET Framework** Versions but we not can "opt-out" of using NET Framework.
- `Analyzer` (main project), `Analyzer.Codefixes`, `Analyzer.Package` Projects are using the to be expected `netstandard2.0` in `.csproj` that doesn't applies on the two other provided Projects!
- `Analyzer.Test` is provided with the *expected to be fixed and by that not included* `netcoreapp3.1`
- `Analyzer.Vsix` is provided with the previously *required to be selected* `net472`

There is exactly **NO** Information about both (Framework / .NET Core) installation Components would be required for this tutorial or using the Roslyn SDK Templates, I would ask you to add those critical information into this Documentation and, if you have some, also to suggest to us, how to workaround this or similar. But saying nothing and just awaiting the user to get a bad User Expirience is the worst approach I can think of 👀
and I am sure, that's not your intention 👍

**This is the current User Expirience you are providing to us without any changes:**

https://github.com/user-attachments/assets/55ed18de-a600-4d63-82dd-4dfa351d89c2

Since the linked sample *is not using these issued TFM's*, I think someone is aware of this update requirement in your Team and maybe even if you are not the ones relyable for the Tempaltes provided, you could possibly add a kind of migration/Troubleshooting section for this?
Thanks in advance!

## Additional Information & Feedback

I did hear already from the requirement to be using `netstandard2.0` even if I am not very happy about it, because we are now for regular apps at .NET 10, that would be okay and expected.
Even Visual Studio Installer itself is stating `.NET Core 3.1-Runtime` as not longer supported so the priority of anyone who is maybe relyable in shipping VS Templates should maybe re-evaluated 😄 :

### Page URL

https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/tutorials/how-to-write-csharp-analyzer-code-fix

### Content source URL

https://github.com/dotnet/docs/blob/main/docs/csharp/roslyn-sdk/tutorials/how-to-write-csharp-analyzer-code-fix.md

### Document Version Independent Id

a286e20b-1e43-dc57-e0fb-5a9dee7ec3f6

### Platform Id

66b66ae2-c045-6e7a-3fc2-550b1ac424ee

### Article author

@BillWagner

### Metadata

* ID: 6e3fc905-7aa1-7f5e-9bfe-fbcef461ad5e
* PlatformId: 66b66ae2-c045-6e7a-3fc2-550b1ac424ee
* Service: **dotnet-csharp**
* Sub-service: **roslyn-sdk**

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