Implement interactive prop handling for StickmanRig

- Added PropTrajectory class for deterministic ballistic calculations.
- Introduced StickmanPropInteraction component to manage prop interactions (pickup, drop, throw).
- Implemented grip resolution and attachment logic for props.
- Added signals for interaction events (prop_picked_up, prop_dropped, prop_thrown).
- Defined specifications for prop interaction lifecycle and event rules.
- Ensured compatibility with existing prop systems and added new capabilities for prop pickup.

scripts/prop_file.gd

@@ -62,7 +62,7 @@ static func sanitize_shape(shape: Dictionary, grid_size: float = TerrainUtilsScr
 	return result
 
 
-static func to_file_dict(prop_name: String, material_preset: int, shapes: Array[Dictionary], anchors: Dictionary = {}) -> Dictionary:
+static func to_file_dict(prop_name: String, material_preset: int, shapes: Array[Dictionary], anchors: Dictionary = {}, can_be_picked_up: bool = true) -> Dictionary:
 	var serialized: Array = []
 	for shape: Dictionary in shapes:
 		serialized.append(_serialize_shape(shape))
@@ -73,6 +73,7 @@ static func to_file_dict(prop_name: String, material_preset: int, shapes: Array[
 		"material_preset": preset_to_string(material_preset),
 		"shapes": serialized,
 		"anchors": PropAnchorDataScript.serialize_anchors(anchors),
+		"can_be_picked_up": can_be_picked_up,
 		"metadata": {"created_at": now, "modified_at": now},
 	}
 
@@ -108,6 +109,7 @@ static func from_file_dict(data: Variant) -> Dictionary:
 		"material_preset": preset,
 		"shapes": shapes,
 		"anchors": PropAnchorDataScript.normalize_anchors(dict.get("anchors", {})),
+		"can_be_picked_up": dict.get("can_be_picked_up") if dict.get("can_be_picked_up") is bool else true,
 	}