HSTS_MAX_AGE, a Go duration, sets the max-age of the
Strict-Transport-Security header. Unset, it is ten years (87600h);
0 sends no header at all. A negative value, or one that is not a
whole number of seconds, stops startup like an unparseable one.
includeSubDomains and preload stay in the header. The value is shown
on /settings and in the startup log, and the README's HSTS section
now says what each part of the header commits the operator to.
Model: opus-5-5
sneak