docs(0.S): the doc fences migrated by ludic migrate state; LANGUAGE.md's state section says what the tool and the checker do now; no module-level var left in the docs

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

docs/language/phases/phase-overlay.md

@@ -17,7 +17,7 @@ program OverlayExample {
   model Player { Position }
 
   const TILE_SIZE: int = 16
-  var score: int = 0
+  let score: int = 0
 
   handler PlacePlayer phase Start {
     spawn Player { Position { column: 5, row: 6 } }