Add new scene files and implement stage impact resolver

- Created three new scene files: `wobble.scene`, `wobble2.scene`, and `wobble3.scene` with various terrain and prop configurations.
- Introduced `stage_impact_resolver.gd` script to manage impact detection and response between props and stickmen.
- Added unit tests for actor blocking overlap to ensure proper interaction with stationary props.

sandbox_theme.json

@@ -70,6 +70,13 @@
     "play": "#33DD77",
     "guide": "#22C6FF"
   },
+  "effects": {
+    "impact_wobble": {
+      "duration": 0.48,
+      "maximum_angle_degrees": 7.0,
+      "sideways_offset": 4.0
+    }
+  },
   "grid": { "snap_size": 15.0 },
   "chrome": {
     "style_defaults": { "bg_color": "#171B24F2", "corner_radius": 10 },