Call state handling, max‑calls enforcement, and tone playback are inconsistent with multiple simultaneous…

Call state handling, max‑calls enforcement, and tone playback are inconsistent with multiple simultaneous…: a task in LegoFlow-SWE (Harbor dataset). When there are several concurrent calls (across one or more user‑agents) and when calls transition through progress / established / terminated…

The task

When there are several concurrent calls (across one or more user‑agents) and when calls transition through progress / established / terminated states, a number of related problems appear:

Part of Lego-X/LegoFlow-SWE.