The existing filters don't cover incomplete reminders without due dates.
`upcoming` requires a due date, so undated items (e.g. grocery lists)
are only visible via `all` which includes completed items too.
`remindctl open` returns all uncompleted reminders regardless of
due date status.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
(cherry picked from commit c5019fd566da5861dafc932d4ca9792cf33b6e46)
