Idiot enforces its card (rev 23) + attack sight-line tracing

Rules rev 23 — IDIOT, per the card and FAQ:
- No handling items: pick up / drop of treasures and objects refused
  (dropping was the exploit: capturing a stolen treasure on your own home,
  or dropping your own treasure underfoot for an instant cure)
- No punching, no thrown dagger / large rock (attacks on players)
- No effect on a victim already carrying one of their own treasures
Ungated (permissive): counteractions are now castable while idiotized (the
one thing the card expressly allows — the gate wrongly blocked them), and
goal-aiding spells (IDIOT_AIDS: destroy-wall, teleport, mad-dash, ...) per
the FAQ's 'you could, however, destroy a wall'.

Sight tracing: while an LOS attack sits on the stack, the board draws the
line it traveled — straight when direct, leg by leg through both warp
mouths (with pulsing rings) when the maze's wraparound carried it. Engine
traceSight/traceSightFor/stackSightTrace; overlay in Board.svelte; shown
live and in replays. Verified against H3PC's cross-board Idiot cast.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0138A8CjeQRpvzKxuMfz1Bqc

packages/engine/src/view.ts

@@ -2,8 +2,8 @@
 // The server sends this after every state change; clients never see the
 // deck order or other players' hands.
 
-import { sightBetween, type AssembledBoard } from "./board";
-import { type CardInstance } from "./cards";
+import { sightBetween, traceSight, type AssembledBoard, type Cell, type SightTrace } from "./board";
+import { cardDef, type CardInstance } from "./cards";
 import {
   boardView,
   LOS_BLOCKING_CONTENT,
@@ -173,6 +173,16 @@ export function sightedCellsFor(view: GameView): Set<string> {
   const out = new Set<string>();
   const me = view.players.find((p) => p.id === view.you);
   if (!me) return out;
+  const { board, blockers } = sightBasis(view);
+  for (const key of Object.keys(board.cells)) {
+    const [x, y] = key.split(",").map(Number) as [number, number];
+    if (sightBetween(board, me.position, { x, y }, blockers)) out.add(key);
+  }
+  return out;
+}
+
+/** The board-as-seen and sight blockers this view's sight rules run against. */
+function sightBasis(view: GameView): { board: GameView["board"]; blockers: Record<string, true> } {
   // Held-open doors are open doorways to the eye (rules rev 15).
   let board = view.board;
   if (view.deckRev >= 15 && view.heldDoorEdges.length > 0) {
@@ -189,11 +199,38 @@ export function sightedCellsFor(view: GameView): Set<string> {
       blockers[`${p.position.x},${p.position.y}`] = true;
     }
   }
-  for (const key of Object.keys(board.cells)) {
-    const [x, y] = key.split(",").map(Number) as [number, number];
-    if (sightBetween(board, me.position, { x, y }, blockers)) out.add(key);
-  }
-  return out;
+  return { board, blockers };
+}
+
+/**
+ * How one square sees another under this viewer's knowledge of the board
+ * (believed illusion walls block; held doors admit). Null when no sight
+ * exists — the renderer's material for drawing the line an attack traveled.
+ */
+export function traceSightFor(view: GameView, from: Cell, to: Cell): SightTrace | null {
+  const { board, blockers } = sightBasis(view);
+  return traceSight(board, from, to, blockers);
+}
+
+/**
+ * The sight line behind the attack currently on the stack — the board's
+ * answer to "how can he even see me?". Null when nothing should draw:
+ * no stack, a creature's or physical attack, a non-LOS card, attacker and
+ * defender sharing a square, or no sight under this viewer's knowledge
+ * (a believed illusion wall can honestly hide the line).
+ */
+export function stackSightTrace(
+  view: GameView,
+): { from: Cell; to: Cell; trace: SightTrace } | null {
+  const stack = view.stack;
+  if (!stack || stack.creatureId) return null;
+  if (!stack.attackCard || cardDef(stack.attackCard.cardId).los !== true) return null;
+  const a = view.players.find((p) => p.id === stack.attackerId);
+  const d = view.players.find((p) => p.id === stack.defenderId);
+  if (!a || !d) return null;
+  if (a.position.x === d.position.x && a.position.y === d.position.y) return null;
+  const trace = traceSightFor(view, a.position, d.position);
+  return trace ? { from: a.position, to: d.position, trace } : null;
 }
 
 const CREATION_CARD_IDS = new Set([