Refactor rhythm action architecture

resources/beat_chart.gd

@@ -0,0 +1,27 @@
+class_name BeatChart
+extends Resource
+
+@export var chart_id: StringName = &""
+@export var total_beats := 0
+@export var tracks: Array = []
+
+
+func all_events() -> Array:
+	var result: Array = []
+	for track in tracks:
+		if not track is Resource:
+			continue
+		for event in track.call("sorted_events"):
+			result.append(event)
+	result.sort_custom(func(a: Resource, b: Resource) -> bool:
+		var a_position := float(a.call("beat_position"))
+		var b_position := float(b.call("beat_position"))
+		if is_equal_approx(a_position, b_position):
+			return str(a.get("event_type")) < str(b.get("event_type"))
+		return a_position < b_position
+	)
+	return result
+
+
+func is_empty() -> bool:
+	return all_events().is_empty()