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.
Introduces a 3-phase algorithm in `EventStackManager` for dynamic event positioning. Groups events by start time proximity to determine optimal layout.
Optimizes horizontal space by using side-by-side grid columns for simultaneous events and allowing non-overlapping events to share stack levels. Supports nested stacking for late-arriving events within grid columns.
Includes comprehensive documentation (`STACKING_CONCEPT.md`) and a visual demonstration (`stacking-visualization.html`) to explain the new layout logic. Updates event rendering to utilize the new manager and adds extensive test coverage.
