Form validation notifications should not disappear

This issue is about the accessibility of the notification self-hiding at all. As well as being a poor UX generally, this is potentially an issue for users experiencing distraction (that's everyone) or of limited vision.

• Am creating a CiviMail while in Mountain TZ
• Server is in Pacific/Auckland TZ, so several hours ahead
• When I try to send, I see screen attached
• "Send mail" button is disabled, notification says "The selected time is in the past"
• Notification disappears quickly and leaves no way to show notifications

IMO form validation failures should never self-hide, since they remove information important to the context of why the form submission will not proceed. (See attached screen - no clue remains why the submit button is disabled.)

Perhaps auto-hiding notifications was proposed in response to user weariness at seeing too many notifications, but I don't think it's the right choice & hope this example illustrates why I feel that way

(If anyone can find the ticket where this behaviour was introduced I'd like to read the original proposal.)