Kruiswoordpuzzel

A crossword. The booklet prints the clues under "Horizontaal" and "Verticaal"
(numbered automatically); the answer sheet has the grid, one letter box per
cell. Each word is graded on its own: all its letters right is one point.

Give each word its start cell (`row`, `col`, counted from 1 at the top left)
and `direction`. Validation checks that crossing words share the same letter
and that no letters touch by accident (every run of two or more letters must
be one of the words). Letters A-Z only; write IJ as two letters.

`secret` shades cells whose letters, in the given order, spell a hidden word;
ask for it in a separate `short-text` task.