The single-column grid used the implicit auto track, which grows to the
widest cell's min-content. The draw date's date and time inputs size
from the font, so with wider metrics that min-content passed the dialog
body (about 422 px against 398 px) and the value input ran 24 px into
the dialog's padding. An explicit grid-cols-1 track is minmax(0, 1fr)
and stays at the body's width; the date row already shrinks inside it.
Refs #1214