Rev 19: a dust cloud blinds whoever stands in it (CPU7)

The automaton stood in Kestrel's DUST CLOUD and filled a square with
stone three rows away. The cloud blocked only sight lines passing
through it; the square a line began or ended in was never asked. The
FAQ is plain: no LOS spell may be cast by a wizard in a cloud, nor at
one, though a spell upon oneself still works, and VISIONSTONE does
not see through dust. From rev 19 the engine's sight and the view's —
the targeting aid the client and the automaton both read — refuse a
line with dust at either end. Older games keep their sight.

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

packages/engine/test/expansion-terrain.test.ts

@@ -145,6 +145,29 @@ describe("expansion terrain", () => {
     }
   });
 
+  it("a wizard in a dust cloud casts no LOS spell out, and none reaches them (rev 19)", () => {
+    for (const deckRev of [19, 18]) {
+      let { state } = createGame({ playerIds: ["alice", "bob"], seed: 42, sets: ["basic", "expansion1"], deckRev });
+      const me = activePlayer(state);
+      const spot = emptyNeighborCell(state, me.position);
+      state.squareContents[cellKey(spot.cell)] = { kind: "dust", damage: 0, createdBy: me.id };
+      me.position = { ...spot.cell };
+      // An empty square beside the cloud, in plain sight but for the dust.
+      const outside = emptyNeighborCell(state, spot.cell).cell;
+      const blind = deckRev >= 19;
+      expect(gameLos(state, me.position, outside, me.id)).toBe(!blind);
+      expect(gameLos(state, outside, me.position)).toBe(!blind);
+      expect(gameLos(state, me.position, me.position, me.id)).toBe(true);
+      const sighted = sightedCellsFor(viewFor(state, me.id));
+      expect(sighted.has(cellKey(outside))).toBe(!blind);
+      expect(sighted.has(cellKey(me.position))).toBe(true);
+      // FILL SQUARE WITH STONE from inside the cloud: refused when blind.
+      const stone = giveCard(state, me.id, "fill-square-with-stone");
+      const r = applyCommand(state, me.id, { type: "cast", instanceId: stone.instanceId, target: { kind: "cell", cell: outside } });
+      expect(r.ok).toBe(!blind);
+    }
+  });
+
   it("glue pins a treasure to the floor until it wears off", () => {
     let { state } = newGame();
     const me = activePlayer(state);