Todos snoozing UX tweaks

This follows up on #17712 (closed) which was completed but had a few minor follow-up items remaining.

• Revisit the timestamps' display as per !175117 (comment 2277691962).
• Resolving a todo keeps it visible till the auto-refresh kicks in, but snoozing a todo hides it immediately... Could we also keep it around, to keep things consistent?