Source generator should ensure hint names are unique

[jjonescz]

Version used: .NET v9.0.200

Steps to reproduce:

1. Create file Components/Counter.razor.
2. Create file Components_Counter.razor.
3. Compile.

Actual Result:

CSC : warning CS8785: Generator 'RazorSourceGenerator' failed to generate source. It will not contribute to the output and compilation errors may occur as a result. Exception was of type 'ArgumentException' with message 'The hintName 'Components_Counter_razor.g.cs' of the added source file must be unique within a generator. (Parameter 'hintName')'.

Expected Result:

Either

• a better error message, or
• success.