feat(items): add HoldableItem with hand slot detection, fix detach_item position

- Character registers in "characters" group on _ready for group scanning
- detach_item saves/restores global_position after reparenting
- New HoldableItem base class: scans "characters" group on drag_released,
  attaches to nearest free hand within 60px radius, detaches on pickup

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

scripts/objects/holdable_item.gd

@@ -0,0 +1,73 @@
+## HoldableItem — Node2D that can be held in a Character's HandLeft or HandRight slot.
+## Attach DragDropComponent as a child. On drag_released scans "characters" group for
+## the nearest free hand slot within HAND_SLOT_RADIUS.
+class_name HoldableItem extends Node2D
+
+signal item_picked_up(item: HoldableItem)
+signal item_placed(item: HoldableItem)
+
+const HAND_SLOT_RADIUS: float = 60.0
+
+@export var item_id: String = ""
+
+
+func _ready() -> void:
+	var drag: DragDropComponent = get_node_or_null("DragDropComponent") as DragDropComponent
+	if drag != null:
+		drag.drag_picked_up.connect(_on_drag_picked_up)
+		drag.drag_released.connect(_on_drag_released)
+
+
+func _on_drag_picked_up(_pos: Vector2) -> void:
+	if is_in_hand_slot():
+		_detach_from_hand_slot()
+	item_picked_up.emit(self)
+
+
+func _on_drag_released(_pos: Vector2) -> void:
+	var result: Array = _find_nearest_free_hand_slot()
+	if not result.is_empty():
+		var character: Character = result[0] as Character
+		var hand: String = result[1] as String
+		character.attach_item(hand, self)
+	item_placed.emit(self)
+
+
+func is_in_hand_slot() -> bool:
+	var p: Node = get_parent()
+	if p == null:
+		return false
+	return p.name == "HandLeft" or p.name == "HandRight"
+
+
+func _detach_from_hand_slot() -> void:
+	var hand_slot: Node = get_parent()
+	var character: Character = hand_slot.get_parent() as Character
+	if character == null:
+		return
+	var hand: String = "left" if hand_slot.name == "HandLeft" else "right"
+	character.detach_item(hand)
+
+
+func _find_nearest_free_hand_slot() -> Array:
+	var best_dist: float = HAND_SLOT_RADIUS
+	var best_character: Character = null
+	var best_hand: String = ""
+	for node: Node in get_tree().get_nodes_in_group("characters"):
+		var character: Character = node as Character
+		if character == null:
+			continue
+		for hand: String in ["left", "right"]:
+			if not character.is_hand_free(hand):
+				continue
+			var slot: Node2D = character.get_node_or_null("Hand" + hand.capitalize()) as Node2D
+			if slot == null:
+				continue
+			var dist: float = global_position.distance_to(slot.global_position)
+			if dist < best_dist:
+				best_dist = dist
+				best_character = character
+				best_hand = hand
+	if best_character == null:
+		return []
+	return [best_character, best_hand]