parseRobots accepted 2027-02-30 (Date.parse rolls it over) and refused
max-snippet:+5, both unlike classes/robots_value.go. A value it could not
parse showed every group as Inherit and the first click serialised the
empty model, dropping the stored directives. Dates are now checked as
calendar dates, a sign is accepted, and an unparsed value is kept with a
note, the controls off and an explicit Reset.
Jakub Zych
923d0f9c3a