Moves complex layout determination logic (grid grouping, stack levels, positioning) from `EventRenderer` to a new `EventLayoutCoordinator` class.
Delegates layout responsibilities to the coordinator, significantly simplifying the `EventRenderer`'s `renderColumnEvents` method. Refines `EventStackManager` by removing deprecated layout methods, consolidating its role to event grouping and core stack level management.
Improves modularity and separation of concerns within the rendering pipeline.
