feat: implement damage dummy system, floating UI numbers, and double-barrel shotgun mechanics

debug/test_level_builder.gd

@@ -31,6 +31,7 @@ func _build_geometry() -> void:
 	_build_platforms()
 	_build_wall_run_corridor()
 	_build_speed_corridor()
+	_build_target_dummy()
 	_build_lighting()
 	_build_player()
 
@@ -207,6 +208,15 @@ func _build_speed_corridor() -> void:
 		_box_static(Vector3(34, 0.15, float(i)), Vector3(8, 0.3, 0.5), Color(0.8, 0.8, 0.2), "SpeedBump_%d" % i)
 
 
+# ── Dummies ───────────────────────────────────────────────────────────────────
+
+func _build_target_dummy() -> void:
+	var dummy = load("res://entities/target_dummy.gd").new()
+	dummy.name = "TargetDummy"
+	# Place it somewhat centrally in the main arena, but out of the immediate spawn area
+	dummy.position = Vector3(0, 0, -10)
+	add_child(dummy)
+
 # ── Lighting ──────────────────────────────────────────────────────────────────
 
 func _build_lighting() -> void: