feat: performance budget profiling setup

- docs/performance-budget.md: 60fps/2GB VRAM budget with CPU, GPU,
  memory, and draw-call targets (P95<16.6ms, P99<50ms)
- scripts/profiling/: SceneTree + Node profilers, test scenes
- scripts/generate_occluders.gd: auto-generate OccluderInstance3D
  from CSG wall pieces (128^3 voxel occlusion culling)
- scripts/convert_csg_to_mesh.gd: CSG->StaticMesh baker with LOD
  slots (LOD1@15m, LOD2@30m)
- project.godot: occlusion culling + LOD settings enabled
- modular scene UV2 data from lightmapping pass
- rcon_command_handler.gd conflict resolved (kept upstream plugin cmd)
- Fixed profiler_node.gd warmup frame bug (60 frames, not 3)
- Fixed convert_csg_to_mesh.gd LOD API (add_lod + distance)

client/scripts/profiling/test_process.gd

@@ -0,0 +1,21 @@
+extends SceneTree
+
+func _init():
+	print("_init called")
+	# Add a simple node to trigger processing
+	var n = Node.new()
+	n.name = "test"
+	n.set_process(true)
+	root.add_child(n)
+	print("Node added")
+
+func _process(delta: float) -> bool:
+	print("_process called: delta=", delta)
+	if frame_count > 5:
+		print("Quitting after 5 frames")
+		quit(0)
+		return true
+	frame_count += 1
+	return true
+
+var frame_count := 0