fix(offline): hotseat finished-game medals by final score (fix all-last-place on a tie)

Reported: a hotseat game ended by 6 scoreless passes deducts each rack
(correct rule, same as online: -8/-14/-8 here), which tied two seats for
the lead. The engine's winner() returns -1 on a tie, so seatMedal read it
as a full draw and gave EVERY seat the last-place medal.

- result.ts: seatMedal now ranks by the FINAL score (competition ranking —
  a tie for the lead shares the trophy), not the single-winner flag. A
  resigned / host-excluded seat places last with no medal and does not push
  the others down.
- model.ts: Seat.resigned (offline-only); engine.resignedOf getter; the
  local source surfaces it on the game view.
- The scoreless rack deduction is unchanged (standard rules, owner-confirmed).

ui/src/lib/model.ts

@@ -29,6 +29,9 @@ export interface Seat {
   score: number;
   hintsUsed: number;
   isWinner: boolean;
+  /** Offline hotseat only: the seat resigned or was excluded by the host. Set by the local source so
+   *  the finished-game medal ranking can place it last (no medal); undefined for online seats. */
+  resigned?: boolean;
 }
 
 export interface GameView {