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_library.gd

@@ -75,7 +75,7 @@ static func make_custom_entry(path: String) -> Dictionary:
 	var name := String(parsed.get("prop_name", "")).strip_edges()
 	if name.is_empty(): name = normalized_path.get_file().get_basename()
 	var preset: int = int(parsed.get("material_preset", PROP_BLOCK.MaterialPreset.NONE))
-	return {"id": normalized_path, "path": normalized_path, "name": name, "material_preset": preset, "material_label": PROP_FILE.preset_to_string(preset).capitalize(), "is_custom": true, "payload": PROP_FILE.flatten_to_payload(shapes), "shapes": shapes, "collision_hull": hull}
+	return {"id": normalized_path, "path": normalized_path, "name": name, "material_preset": preset, "material_label": PROP_FILE.preset_to_string(preset).capitalize(), "is_custom": true, "payload": PROP_FILE.flatten_to_payload(shapes), "shapes": shapes, "collision_hull": hull, "anchors": parsed.get("anchors", {}), "can_be_picked_up": bool(parsed.get("can_be_picked_up", true))}
 
 
 static func is_custom_path(path: String) -> bool:
@@ -110,4 +110,6 @@ static func _make(id: String, name: String, preset: int, label: String, payload:
 		"path": "",
 		"shapes": [],
 		"collision_hull": PackedVector2Array(),
+		"anchors": {},
+		"can_be_picked_up": true,
 	}