Add prop interaction system and throw mechanics specification

- Introduced `stickman_prop_interactor.gd` to manage prop interactions.
- Created `phase_11_prop_interactions.md` detailing the design and implementation of prop pickup, drop, and throw mechanics.
- Defined interaction states, action lifecycles, and event triggers for prop handling.
- Specified constraints for throw actions, including target positioning and velocity calculations.
- Established acceptance criteria for prop interactions and lifecycle management.

scripts/missing_prop_placeholder.gd

@@ -3,11 +3,13 @@ extends Node2D
 
 var original_entry: Dictionary = {}
 var missing_prop_path: String = ""
+var stage_object_id: String = ""
 const MARKER_SIZE := Vector2(180.0, 54.0)
 
 func configure(entry: Dictionary) -> void:
 	original_entry = entry.duplicate(true)
 	missing_prop_path = String(entry.get("asset_id", ""))
+	stage_object_id = String(entry.get("stage_object_id", ""))
 	queue_redraw()
 
 func get_area_rect() -> Rect2: