OptionalcontainerDOM container; defaults to document.body.
The player whose schedule is rendered. The panel two-way-binds
to the player: the player's onDateChanged updates the cursor;
dragging the cursor or clicking a milestone calls back into the
player's setDateMs / nextMilestone / play / pause.
OptionalstoragelocalStorage key for persisting drag position + closed state.
Defaults to "xkt-sch-panel".
OptionalvisibleShow on construction (default true).
Constructor parameters for SchedulePanel.