chore(prototype): add in-game vehicle probe game script

Throwaway probe for "Probe vehicle data and native passing in game":
logs every player-owned road vehicle's MovePath/LandVehicle/move-info
state every 5s and groups vehicles by street segment to expose lanes
and oncoming traffic.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

mod/content/overtake_probe.gs.lua

@@ -0,0 +1,8 @@
+-- PROTOTYPE (ticket "Probe vehicle data and native passing in game"): throwaway, lives only on branch prototype/vehicle-probe.
+function data()
+	return {
+		updateScript = {
+			fileName = "overtake_probe.script@update",
+		},
+	}
+end