refreshSessionDerived's dep array referenced refreshActiveFix and
schedulePreviewRefresh before they were declared. React evaluates
useCallback deps synchronously during render, so the page blew up with
"Cannot access 'refreshActiveFix' before initialization" before a single
render completed. Moved the three leaf helpers above the aggregator.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>