Type vlayer forward declarations and config entries

The gui element locals are declared at the top and assigned far below,
so emmylua inferred them as nil at every use site.

circuit_oc was reassigned from a control behaviour to a logistic
section, which hid every section method behind the wrong type.

allowed_items entries carry heterogeneous optional properties, now
described by a class.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

exp_legacy/module/modules/control/vlayer.lua

@@ -14,10 +14,10 @@ local mega = 1000000
 local vlayer = {}
 local vlayer_data = {
     entity_interfaces = {
-        energy = {},
-        circuit = {},
-        storage_input = {},
-        storage_output = {},
+        energy = {}, --- @type LuaEntity[]
+        circuit = {}, --- @type LuaEntity[]
+        storage_input = {}, --- @type LuaEntity[]
+        storage_output = {}, --- @type LuaEntity[]
     },
     properties = {
         total_surface_area = 0,
@@ -582,11 +582,11 @@ local function handle_circuit_interfaces()
         if not interface.valid then
             vlayer_data.entity_interfaces.circuit[index] = nil
         else
-            local circuit_oc = interface.get_or_create_control_behavior()
-            if circuit_oc.sections_count == 0 then
-                circuit_oc.add_section()
+            local control = interface.get_or_create_control_behavior()
+            if control.sections_count == 0 then
+                control.add_section()
             end
-            circuit_oc = circuit_oc.sections[1]
+            local circuit_oc = control.sections[1]
             local signal_index = 1
             local circuit = vlayer.get_circuits()