Rev 17: a warp mouth on a pit's rim is a way off it (M4Q7)

Kestrel stood beside a pit dug against the board's west edge, walls
north and south of it, and was told there was nothing to land on — the
rim check counted only neighbouring squares, and the warp mouth beyond
the pit is not one. From rev 17 a mouth on the rim is an exit like any
square, named at a fork like any other; every older game takes the
mouth when no square offers, so the refused crossing goes through as
it stands. The jump through a mouth carries `via: "warp"`: the board
shimmers both mouths instead of streaking across the maze, and the
reel cuts rather than gliding. The automaton leaves a pit only by its
exits. Three tests walk the rim under both readings.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jm2auWk6RP71CjaAb4FMoG

packages/engine/src/automaton.ts

@@ -592,14 +592,22 @@ function wallBlastTarget(
 /** Can a wizard entering the pit at `pit` heading `dir` get off its rim
  * — the maze's own test: some side other than the way back with a cell
  * there, no wall between, and no stone on it. */
+/** The sides a walker may leave a pit by, having entered it heading
+ * `dir`: neighbouring squares first; a warp mouth on the rim only when
+ * no square offers, the reading every revision accepts. */
+function pitExits(view: GameView, pit: Cell, dir: Side): Side[] {
+  const footing = (d: Side) => {
+    if (d === opposite(dir)) return null;
+    const t = stepTarget(view.board, pit, d);
+    if (t.kind === "blocked" || view.squareContents[cellKey(t.to)]?.kind === "stone") return null;
+    return t.kind;
+  };
+  const floor = SIDES.filter((d) => footing(d) === "step");
+  return floor.length > 0 ? floor : SIDES.filter((d) => footing(d) === "warp");
+}
+
 function pitLandable(view: GameView, pit: Cell, dir: Side): boolean {
-  return SIDES.some((d) => {
-    if (d === opposite(dir)) return false;
-    const beyond = neighbor(pit, d);
-    return !!view.board.cells[cellKey(beyond)] &&
-      (view.board.edges[edgeKey(pit, d)] ?? "open") === "open" &&
-      view.squareContents[cellKey(beyond)]?.kind !== "stone";
-  });
+  return pitExits(view, pit, dir).length > 0;
 }
 
 export function pathToward(
@@ -632,6 +640,11 @@ export function pathToward(
         // direction; with nothing to land on, the maze bounces the leaper
         // back and charges the stride. Goal or waypoint, that is no road.
         if (hazard === "pit" && !pitLandable(view, to, dir)) continue;
+        // Out of a pit only by one of its exits.
+        if (view.squareContents[cellKey(c)]?.kind === "pit") {
+          const entry = cameBy.get(cellKey(c))?.dir;
+          if (entry && !pitExits(view, c, entry).includes(dir)) continue;
+        }
         seen.add(k);
         cameBy.set(k, { prev: cellKey(c), dir, viaDoor });
         if (goals.has(k)) { found = k; break; }