Tracks the cog_pipeline corpus bump from 2 → 3 (year=2012 partition is now modern-only; v2 shipped a broken mixed-source partition). session open aborts with a clear message if a reader hits a legacy v2 corpus.
Tracks the cog_pipeline corpus bump from 2 → 3 (year=2012 partition is now modern-only; v2 shipped a broken mixed-source partition). session open aborts with a clear message if a reader hits a legacy v2 corpus.