feat: complete mobile UI implementation

project/help_ui_test.gd

@@ -113,3 +113,13 @@ func _run() -> void:
 	_ck(is_instance_valid(sm.help_ui), "SystemMenuUI.open_help() lazily builds help_ui")
 	_ck(sm.help_ui.is_open(), "SystemMenuUI.open_help() opens the help window")
 	sm.help_ui.close()
+
+	# 移动端帮助页使用横屏滚动布局，不能把 PC 帮助图缩到不可读。
+	ui.set_mobile_mode(true)
+	hw.set_mobile_mode(true)
+	hw.open()
+	_ck(hw.is_open() and hw._mobile_root.size == Vector2(760, 340),
+			"mobile help window uses landscape base size")
+	_ck(hw.rows().size() == 19 and not hw.rows()[0].begins_with("<"),
+			"mobile help keeps all localized rows")
+	hw.close()