Done. The December 2025 monthly business review narrative is saved at `output/mbr-narrative.md`. It covers December results ($827K revenue, $8K operating income vs. $824K budget and $13K budget), the year-to-date performance ($11.2M revenue vs. $11.6M budget, $388K operating income vs. $583K budget), the four largest line variances, and four KPIs off target. All figures are sourced directly from the script output and traceable to the input files.