Add scenes, static scene-finding mechanism, and scene pool for visual hold/tap notes.

rhythm_game/note/visual/tap/tap_note.gd

@@ -0,0 +1,9 @@
+class_name TapNote extends NoteVisual
+
+var id: int = -1
+
+func reset() -> void:
+	id = -1
+
+func in_use() -> bool:
+	return id >= 0

rhythm_game/note/visual/tap/tap_note.gd.uid

@@ -0,0 +1 @@
+uid://1qve2pqu1yr4

rhythm_game/note/visual/tap/tap_note.tscn

@@ -0,0 +1,21 @@
+[gd_scene format=3 uid="uid://jbgxbhfpj806"]
+
+[ext_resource type="Script" uid="uid://1qve2pqu1yr4" path="res://rhythm_game/note/visual/tap/tap_note.gd" id="1_kuk3o"]
+
+[node name="TapNote" type="Node2D" unique_id=1341974559]
+script = ExtResource("1_kuk3o")
+metadata/_custom_type_script = "uid://1qve2pqu1yr4"
+
+[node name="ColorRect" type="ColorRect" parent="." unique_id=743279305]
+anchors_preset = 8
+anchor_left = 0.5
+anchor_top = 0.5
+anchor_right = 0.5
+anchor_bottom = 0.5
+offset_left = -29.0
+offset_top = -6.0
+offset_right = 29.0
+offset_bottom = 6.0
+grow_horizontal = 2
+grow_vertical = 2
+color = Color(0.928887, 0.8138475, 0, 1)