Destinations are secondary-only, so the flags go on computeSecondaryFlags
rather than computeSchoolFlags. A phase counts as present only when some
pupil group carries categories — an empty block would otherwise open a nav
entry pointing at a section that never renders.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BvdDKvFFSZuMVDH5fEyTob
