A warp mouth is a wallable line — and the tunnel seals whole

Create Wall refused the board-edge openings: no far cell, so "walls
must be created between two spaces". But bricking over a lettered
opening is a classic play, and the far space is the tunnel itself.
A warp mouth now counts as wallable — with the wall raised at BOTH
mouths, since a tunnel has one passage: no walking in from the far
board, no warp sight through a sealed pair, and tearing down either
end reopens both. The client grows edge hitboxes at the perimeter
mouths so the line is clickable at all.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/web/src/Board.svelte

@@ -150,6 +150,19 @@
         boxes.push({ cell: c, side: "S", x: c.x * CELL + 4, y: (c.y + 1) * CELL - 6, w: CELL - 8, h: 12 });
       }
     }
+    // Warp mouths sit on the perimeter, with no far cell: still wallable.
+    const seen = new Set(boxes.map((b) => `${b.cell.x},${b.cell.y},${b.side}`));
+    for (const w of view.board.warps) {
+      const c = w.from.cell;
+      const side = w.from.side;
+      const k = `${c.x},${c.y},${side}`;
+      if (seen.has(k)) continue;
+      seen.add(k);
+      if (side === "E") boxes.push({ cell: c, side, x: (c.x + 1) * CELL - 6, y: c.y * CELL + 4, w: 12, h: CELL - 8 });
+      if (side === "W") boxes.push({ cell: c, side, x: c.x * CELL - 6, y: c.y * CELL + 4, w: 12, h: CELL - 8 });
+      if (side === "S") boxes.push({ cell: c, side, x: c.x * CELL + 4, y: (c.y + 1) * CELL - 6, w: CELL - 8, h: 12 });
+      if (side === "N") boxes.push({ cell: c, side, x: c.x * CELL + 4, y: c.y * CELL - 6, w: CELL - 8, h: 12 });
+    }
     return boxes;
   });