2V3-b: click on the ground to walk; read the terrain attribute map

CScreen::SetCursorPosition and CPythonGraphic::SetCursorPosition are the 40250
bodies, so RenderGame builds the pick ray under the cursor each frame.
CPythonBackground::GetPickingPoint* march that ray as
CMapOutdoor::__PickTerrainHeight does, against the native CMapManager height
(PR_FLOAT_TO_INT's x87 rounding becomes floor); object picking waits for
CMapOutdoor. CMapManager::isAttrOn reads the packed <map>/<xxxyyy>/attr.atr
as CMapOutdoor::isAttrOn + CTerrain::isAttrOn do, and CheckAdvancing with its
collision checkers is verbatim (no map objects are registered yet). All of
this stays in the pending/platform layer and is marked ADAPTED.

port.login_flow clicks the ground below the actor after the key walk. The
actor walks to the picked point (334 cm offline), and the fake server sees
FUNC_MOVE, then FUNC_WAIT. It also checks that the actor's cell is free and
that its terrain block has blocked cells. port.login_live against the real
server passed (key 133 cm, click 296 cm), and python_game_render_test.sh
passes offline. MT_TEST_MODE=python_ui now adds the 3D surface, so the port
route can be played by hand.

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

project/client_main.gd

@@ -36,12 +36,18 @@ func _ready() -> void:
 		get_tree().quit(1 if fail else 0)
 		return
 	# MT_TEST_MODE=python_ui：40250 system.py 的界面直接画在 Godot Canvas 上（PORT-PLAN 2V0-f），
-	# Logo → 登录阶段，可用鼠标键盘操作；app.Exit() 退出进程。
+	# Logo → 登录 → 选人 → 进游戏，RenderGame 的 3D 绘制由 python_3d_surface.gd 画出（2V2-e），
+	# 方向键/鼠标点地走动走 40250 原路径（2V3）；app.Exit() 退出进程。
 	if OS.get_environment("MT_TEST_MODE") == "python_ui":
 		AssetPack.ensure()
 		var surface: Control = preload("res://python_ui_surface.gd").new()
 		surface.name = "PythonUISurface"
 		add_child(surface)
+		# The UI surface runs CPythonApplication::Process in its _process; the 3D surface reads that
+		# frame's draws after it, so it comes second in the tree.
+		var world: Node3D = preload("res://python_3d_surface.gd").new()
+		world.name = "Python3DSurface"
+		add_child(world)
 		var err: String = surface.run_app()
 		if err != "":
 			printerr("python_ui: " + err)