`SelectionHandler` is receiving input from anywhere out of necessity:
19f892687a/osu.Game/Screens/Edit/Compose/Components/SelectionHandler.cs (L119-L125)
Also important is that `BlueprintContainer` will selectively not block
right clicks to make sure they fall through to the
`ContextMenuContainer`:
19f892687a/osu.Game/Screens/Edit/Compose/Components/BlueprintContainer.cs (L122-L126)
But because the whole editor is sharing a `ContextMenuContainer` and
it's at a higher level than both components, we observe here the
playfield's `SelectionHandler` intercepting the right click before it
can reach the `ContextMenuContainer`.
The fix here is similar to what we're already doing in
`TimelineBlueprintContaienr`.
57d88a0ac4