The single long/melted aggregate CSV padded every row with the union of
columns across incompatible feature types, hitting 2.5GB+ with the majority
of cells blank. AggregateExporter replaces it with six wide, rectangular
tables (animals, eeg_timeseries, eeg_events, eeg_duration_summary,
video_timeseries, video_events) -- band power, time-frequency, and epoch
diagnostics merge exactly since they share the same per-chunk window grid.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>