Hi, thanks for the report and the repro project.
This is by design. The com.unity.test-framework.performance package ships its assembly definitions with autoReferenced: false, which means Unity does not automatically wire them into the predefined assemblies (Assembly-CSharp-Editor, etc.). A "loose" script in an Editor/ folder compiles into Assembly-CSharp-Editor, and since predefined assemblies have no .asmdef there is no way to add the missing reference - hence the CS0234.
The fix is to place your test script inside a dedicated assembly definition that explicitly references Unity.PerformanceTesting. The quickest way:
> Test Runner -> right-click EditMode tab -> Create EditMode Test Assembly Folder, then add Unity.PerformanceTesting and Unity.PerformanceTesting.Editor to the asmdef's references.
Closing as By Design. Let us know if you have further questions.