Improve Studio diagnostics for member declaration errors

Studio should show member declaration context for diagnostics reported on declaration lines. For example, a bad property type edited through the property inspector should display as Window1 MyProperty declaration: Unknown type 'KermitTheFrog'. instead of relying only on Window1 Line 3. This makes compiler feedback clearer when Studio is showing member-level editors rather than raw source.\n\n### Source discussion\nhttps://forum.objo.dev/d/241-create-property-with-bad-type-doesnt-give-source-of-error\n\n### Scope notes\nUse existing Studio member metadata from SourceMemberParser and diagnostic adjustment in MainWindowViewModel. Do not add generated-source comments or change the compiler error text. Keep existing method/event body locations such as Window1.Button1.Pressed Line 1 unchanged.\n\n### Internal notes\nStatus: in progress. Implementation is underway for declaration-context display locations in Studio diagnostics.