The client's eye learns the VISIONSTONE

The engine always honored the stone — its bearer casts through exactly
one wall or door — but the targeting shadow never did: sightedCellsFor
kept every square behind a wall dimmed, so the aid told the bearer the
stone wasn't working. The sighted set now retries each unseen square
with a single edge removed, mirroring casterLos; the automaton shares
the function, so bots see through their stones too. Two tests pin the
engine ruling and the client parity.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015RCWSTnb1KYTPyL4GmhGnF

packages/engine/src/view.ts

@@ -200,6 +200,26 @@ export function sightedCellsFor(view: GameView): Set<string> {
     const [x, y] = key.split(",").map(Number) as [number, number];
     if (sightBetween(board, me.position, { x, y }, blockers)) out.add(key);
   }
+  // VISIONSTONE lets its bearer see through exactly one wall or door —
+  // any one — so a square is also sighted if removing a single edge
+  // reveals it, mirroring the engine's casterLos.
+  if (me.displayed.some((c) => c.cardId === "visionstone")) {
+    const unseen = Object.keys(board.cells).filter((k) => !out.has(k));
+    for (const edgeK of Object.keys(board.edges)) {
+      if (unseen.length === 0) break;
+      if ((board.edges[edgeK] ?? "open") === "open") continue;
+      const edges = { ...board.edges };
+      delete edges[edgeK];
+      const opened = { ...board, edges };
+      for (let i = unseen.length - 1; i >= 0; i--) {
+        const [x, y] = unseen[i]!.split(",").map(Number) as [number, number];
+        if (sightBetween(opened, me.position, { x, y }, blockers)) {
+          out.add(unseen[i]!);
+          unseen.splice(i, 1);
+        }
+      }
+    }
+  }
   return out;
 }