[C# 14-Fundamentals and reference]: New Feature - Projectless compile

[BillWagner]

Visual Studio release

None

Link to speclet

• Speclet

Link to Pull request

• PR

New behavior

I'll add more updates early next week. This is a placeholder for docs on dotnet run program.cs and the related #! feature.

Language reference tasks

No response

Everyday C# tasks

No response

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Associated WorkItem - 437194