build(gate): forbid production code from importing authoring tools

The architecture check scans tools/ for duplicate class names and fails
when game/ or content/ references res://tools/. The three tools scripts
drop their global class_name (every caller preloads them), and ADR 0012
records that tools/ depends on the domain only.

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

tools/sites/vehicle_test_terrain_recipe.gd

@@ -1,4 +1,3 @@
-class_name VehicleTestTerrainRecipe
 extends RefCounted
 
 const SiteTerrainBaker = preload("res://tools/site_terrain_baker.gd")

tools/sites/zone1_vigilant_recipe.gd

@@ -1,4 +1,3 @@
-class_name Zone1VigilantRecipe
 extends RefCounted
 
 const SiteTerrainBaker = preload("res://tools/site_terrain_baker.gd")