eafc2566f8
variation_plot: set XTickLabelRotation 0 after xticklabels('auto') so many-day
windows (e.g. unmerge_d0_10, 11 ticks) no longer auto-rotate to vertical; nudge
the y-axis label left for breathing room from the tick numbers. Regenerated all
learning-curve figures.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>