Winning

Three finishing touches: announce a draw, highlight the winning line, and colour the marks.

For the highlight, have the helper return the winning line — the three indices — rather than just the mark. Then a cell knows to light up when its own index is in that line. A draw is “every cell filled, nobody won.” Both are derived from the board:

<const/line=winningLine(board)>
<!-- a cell's background: -->
background:${line?.includes(i) ? "#bbf7d0" : "white"}

Everything stays inline — the cell’s colour, its highlight, and a default cursor once it’s filled or the game is over — all computed from state.

Finish it:

1. Change the helper to return the winning line; derive <const/line=...> and an over flag (a win or a full board).
2. Fold a draw message into the status: winner, then draw, then whose turn it is.
3. In each cell’s style, derive background from line?.includes(i), color from the mark, and cursor from whether the cell is still playable.

A complete game — turns, wins, draws, and a highlight — built from an array, a loop, derived values, and guarded handlers. One app left.