fix endgame glyphs for variant wins - closes #21810

A terminal position with no legal moves and no check was always shown
as stalemate, so atomic explosions, antichess, king of the hill,
racing kings and horde wins got the stalemate glyph. Use the chessops
outcome of the position instead, and don't treat a crazyhouse check
that can be blocked by a drop as mate.

ui/lib/src/game/endgame.ts

@@ -1,9 +1,10 @@
 import type { DrawShape } from '@lichess-org/chessground/draw';
-import type { Outcome } from 'chessops';
+import type { Outcome, Position } from 'chessops';
 import { parseFen } from 'chessops/fen';
 import { makeSquare, opposite } from 'chessops/util';
 
-import { fenColor } from './chess';
+import type { PositionResult } from '@/tree/types';
+
 import { endgameGlyphs } from './glyphs';
 import type { StatusName } from './status';
 
@@ -14,31 +15,24 @@ export interface EndgameResult {
 
 type EndgameNode = {
   fen: FEN;
+  pos: () => PositionResult;
   outcome: () => Outcome | undefined;
-  check: () => boolean;
   dests: () => Dests;
 };
 
+const terminalStatus = (pos: Position, outcome: Outcome): StatusName =>
+  outcome.winner ? (pos.isCheckmate() ? 'mate' : 'variantEnd') : pos.isStalemate() ? 'stalemate' : 'draw';
+
 const endgameResult = (
   node: EndgameNode,
   isLast: boolean,
   gameWinner: Color | undefined,
   gameStatus: StatusName,
 ): EndgameResult => {
-  const isTerminal = node.dests().size === 0,
-    isMate = node.check() && isTerminal,
-    isStalemate = !node.check() && isTerminal,
-    isGameEnd = isLast || isTerminal;
-
-  if (!isGameEnd) return {};
-  return {
-    winner: isMate
-      ? opposite(fenColor(node.fen))
-      : isStalemate
-        ? undefined
-        : (node.outcome()?.winner ?? gameWinner),
-    status: isMate ? 'mate' : isStalemate ? 'stalemate' : gameStatus,
-  };
+  const outcome = node.dests().size === 0 ? node.outcome() : undefined;
+  if (outcome) return { winner: outcome.winner, status: terminalStatus(node.pos().unwrap(), outcome) };
+  if (!isLast) return {};
+  return { winner: node.outcome()?.winner ?? gameWinner, status: gameStatus };
 };
 
 export function endgameShapesForNode(