describe page: a data container over an association prints the association name as its context, not the entity it reaches #1571

Repro (v0.26.0, v0.27.0 and current main; Mendix 11.12.5)

Shop.Order_Customer is a Reference from Shop.Order to Shop.Customer, and Shop.Order_Line is a ReferenceSet from Shop.Order to Shop.OrderLine.

create or modify page Shop.PRB_Ctx ( Title: 'Probe', Layout: Atlas_Core.Atlas_Default, Params: { $Order: Shop.Order } ) {
  dataview dvOuter (DataSource: $Order) {
    dataview dvInner (DataSource: $currentObject/Shop.Order_Customer) {
      dynamictext dt (Content: 'Name {1}', ContentParams: [{1} = Name])
    }
    listview lvLines (DataSource: $currentObject/Shop.Order_Line) { … }
  }
};

The page is correct, and mx check reports 0 errors. describe page prints the context like this:

dataview dvInner (DataSource: $currentObject/Shop.Order_Customer) {
  -- Context: $currentObject (Shop.Order_Customer)
listview lvLines (DataSource: $currentObject/Shop.Order_Line) {
  -- Context: $currentObject (Shop.Order_Line), $lvLines (selection)

The expected output is (Shop.Customer) and (Shop.OrderLine), the entities the associations reach. The same happens for a gallery and a data grid over an association, and from the other side of the association: a list view from the Customer side prints (Shop.Order_Customer) instead of (Shop.Order).

Why it matters

The page works. But the comment tells a human or an agent reading describe that the nested widgets bind an entity named after the association, so anything that resolves attributes against the context looks up the wrong element.

Cause

dataSourceEntityContext (cmd_pages_describe_flowcontext.go) says that "for a database or association source the datasource reference is the entity". That's true for a database source. For an association source, the reference is the association's name. The flow-source case was fixed the same way in 6e59e0e. The stored source already carries the destination (EntityRef.Steps[last].DestinationEntity), which is what alter page's entityFromEntityRef reads.

I have a fix ready and will link the PR.