Gmail emails often have multiple labels - an email in "XYZ" label
typically also has "INBOX". The previous negative filter approach
(-label:inbox -label:sent...) excluded these emails entirely, even when
they had a selected label.
Switched to positive OR filtering: (label:cyz OR label:xyz-visible)
-label:spam... which correctly fetches emails with any of the selected
labels regardless of other labels they have.
This edge case wasn't caught earlier because manual testing with INBOX
selected worked fine - it only surfaced when selecting custom labels
without INBOX.
