fix(cluster): dedupe win/explode positions — bonus freeze when a wild is in multiple clusters

[auraladigital]

Addresses #14 ("game sticks when bonus purchase") — a concrete, reproducible cause of the bonus / free-spin freeze.

Cause

A board cell can legitimately belong to more than one win: a wild substitutes into multiple adjacent clusters, so the cluster math lists that cell in each win's positions. After _.flatten(wins.map(w => w.positions)) the cell appears more than once.

Board.svelte › boardWithAnimateSymbols and TumbleBoard.svelte › tumbleBoardExplode store each position's resolver on the symbol:

await waitForResolve((resolve) => (reelSymbol.oncomplete = resolve));

oncomplete is a single slot. A duplicate position overwrites the first resolver, so the symbol's one complete resolves only the last await — the earlier duplicate's promise never settles, Promise.all never resolves, and the round hangs forever.

It only triggers when an event contains a repeated cell (a wild bridging two clusters), which is why it surfaces in bonus and not base, and why the committed Storybook fixtures (bonus_books.ts — 50 books / 308 winInfo events) don't surface it: none of them happen to contain an overlap. Such events do occur in normal 0_0_cluster sims.

Repro

A winInfo (or tumble) event whose wins share a cell (illustrative shape):

wins: [
  { positions: [{ reel: 0, row: 2 }, { reel: 0, row: 3 }] }, // cluster A, incl. wild (0,2)
  { positions: [{ reel: 0, row: 2 }, { reel: 1, row: 2 }] }, // cluster B, same wild (0,2)
]

(0,2) is awaited twice → the round never returns to idle.

Fix

Dedupe positions by (reel,row) before building the promise array, in both handlers. A cell is one symbol with one oncomplete; awaiting it once is correct and the visuals are unchanged.