fix(poc): resolve evaluator and review findings

- Add RectangleShape2D to Character and InteractiveObject collision areas
- Fix HUD button signal connections in _ready()
- Fix character_placed signal emitting global_position
- Extract DEFAULT_DRAG_RADIUS constant in DragDropComponent
- Type Variant on JSON parsed variable in SaveManager
- Extract music symbol constants in HUD
- Refactor duplicated drag input code in InputManager

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/autoload/InputManager.gd

@@ -11,20 +11,30 @@ var _is_dragging: bool = false
 func _input(event: InputEvent) -> void:
 	if event is InputEventScreenTouch:
 		if event.pressed:
-			_is_dragging = true
-			drag_started.emit(event.position)
+			_emit_drag_started(event.position)
 		else:
-			_is_dragging = false
-			drag_ended.emit(event.position)
+			_emit_drag_ended(event.position)
 	elif event is InputEventScreenDrag:
 		if _is_dragging:
-			drag_moved.emit(event.position)
+			_emit_drag_moved(event.position)
 	elif event is InputEventMouseButton and event.button_index == MOUSE_BUTTON_LEFT:
 		if event.pressed:
-			_is_dragging = true
-			drag_started.emit(event.position)
+			_emit_drag_started(event.position)
 		else:
-			_is_dragging = false
-			drag_ended.emit(event.position)
+			_emit_drag_ended(event.position)
 	elif event is InputEventMouseMotion and _is_dragging:
-		drag_moved.emit(event.position)
+		_emit_drag_moved(event.position)
+
+
+func _emit_drag_started(pos: Vector2) -> void:
+	_is_dragging = true
+	drag_started.emit(pos)
+
+
+func _emit_drag_moved(pos: Vector2) -> void:
+	drag_moved.emit(pos)
+
+
+func _emit_drag_ended(pos: Vector2) -> void:
+	_is_dragging = false
+	drag_ended.emit(pos)