Done. The December 2025 monthly business review narrative is written to `output/mbr-narrative.md`.

**Summary:**
- December revenue reached $827K, slightly ahead of the $824K budget
- Operating income fell to $8K, below the $13K budget, driven by gross margin compression and elevated other operating costs
- Year to date, revenue is $362K short of the $11.6M budget, though COGS ran favorable
- Four KPIs are tracking below target: days sales outstanding has been off for 3 months, on-time delivery for 3 months, customer count for 2 months, and inventory turns for 1 month