Debug page — every level the generator knows, straight from
levelOrder. Each preview shows the board as the player meets it: the
givens standing, the dug squares dark, and the boxes told apart by shade. The
stats are measured from the board rather than sent with it — the givens are
counted and checked against the blanks knob, and the solution is re-checked to
be a proper grid that the givens sit inside. The asset stamp and the PGSDK
flavor belong to the container, not to this game.