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_editor.gd

@@ -110,6 +110,7 @@ var _current_path: String = ""
 var _dirty: bool = false
 var _clipboard: Dictionary = {}
 var _anchors: Dictionary = PropAnchorDataScript.default_anchors()
+var _can_be_picked_up: bool = true
 var _selected_anchor_id: String = ""
 var _thumb: PropThumbnail
 var _thumb_cache: ThumbnailCache
@@ -121,6 +122,7 @@ var _material_section: VBoxContainer
 var _mass_label: Label
 var _friction_label: Label
 var _bounce_label: Label
+var _can_be_picked_up_check: CheckBox
 var _fill_button: ColorPickerButton
 var _outline_button: ColorPickerButton
 var _width_spin: SpinBox
@@ -790,6 +792,8 @@ func _do_new() -> void:
 	_set_whole_prop_resize_enabled(false)
 	_prop_name_edit.text = ""
 	_material_preset = PropBlockScript.MaterialPreset.NONE
+	_can_be_picked_up = true
+	if _can_be_picked_up_check != null: _can_be_picked_up_check.button_pressed = true
 	_preset_option.selected = _material_preset
 	_update_physics_labels()
 	_canvas.clear()
@@ -855,6 +859,13 @@ func _build_inspector() -> void:
 	_material_section.add_child(_mass_label)
 	_material_section.add_child(_friction_label)
 	_material_section.add_child(_bounce_label)
+	_can_be_picked_up_check = CheckBox.new()
+	_can_be_picked_up_check.text = "Can be picked up"
+	_can_be_picked_up_check.button_pressed = _can_be_picked_up
+	_can_be_picked_up_check.toggled.connect(func(enabled: bool) -> void:
+		_can_be_picked_up = enabled
+		_mark_dirty())
+	_material_section.add_child(_can_be_picked_up_check)
 	_update_physics_labels()
 
 	# Selected-shape section
@@ -1454,7 +1465,7 @@ func _check_autosave_recovery() -> void:
 # ---------------------------------------------------------------------------
 
 func _build_json_data() -> Dictionary:
-	return PropFileScript.to_file_dict(_prop_name_edit.text, _material_preset, _canvas.get_shape_data(), _anchors)
+	return PropFileScript.to_file_dict(_prop_name_edit.text, _material_preset, _canvas.get_shape_data(), _anchors, _can_be_picked_up)
 
 
 func _apply_json_data(json: Variant, is_recovery: bool = false) -> String:
@@ -1465,6 +1476,8 @@ func _apply_json_data(json: Variant, is_recovery: bool = false) -> String:
 		return "The file could not be read: unsupported version or malformed data."
 	_prop_name_edit.text = str(model.get("prop_name", ""))
 	_material_preset = int(model.get("material_preset", PropBlockScript.MaterialPreset.NONE))
+	_can_be_picked_up = bool(model.get("can_be_picked_up", true))
+	if _can_be_picked_up_check != null: _can_be_picked_up_check.button_pressed = _can_be_picked_up
 	if _preset_option != null:
 		_preset_option.selected = _material_preset
 		_update_physics_labels()