feat(VoxelGrid): add BTL-OFF rung to V-GRID setting

V-GRID now cycles OFF / ON / BTL-OFF.
BTL-OFF keeps the wireframe off during battles while leaving it
available in the overworld. ON preserves the original behaviour
(wireframe forced on in battles regardless of the row).

main.lua

@@ -474,7 +474,7 @@ end
 --         its own: 3D WORLD is exactly the rows WITHOUT it, so that whole
 --         category empties out under FULL and takes itself off the menu.
 local SETTINGS = {
-  -- ------- the top-level menu -- settings that are about the GAME
+    -- ------- the top-level menu -- settings that are about the GAME
   --
   -- SettingsMenu.ROOT as a `cat` puts a row on the DRAMATIC SHAPE screen
   -- itself rather than inside one of the four categories, which is right
@@ -490,7 +490,7 @@ local SETTINGS = {
     cat = SettingsMenu.ROOT, full = true },
 
   -- ------- 3D WORLD -- the diorama's own knobs, every one of them FULL's
-  { VoxelGrid.setting, "One-pixel wireframe along every voxel edge.",
+  { VoxelGrid.setting, "One-pixel wireframe along every voxel edge. BTL-OFF disables it during battles.",
     cat = "world" },
   { WorldCurve.setting,
     "Bends the world down over the horizon, until a town sits on top of its "