Lab: The estimator and Northdesk's numbers sheet

Module 3 · Lab · About 60 minutes · Needs: lessons 1 to 6 of this module, and the Module 2 lab (or nothing: Step 1 rebuilds Modules 1 and 2)

What you are building

Six lessons turned Joel's target into numbers, each in its own notebook: traffic, tokens, sizing, cost, latency and the structural cost choices. Helen wants them on one page she can trust, and Gareth wants to regenerate that page himself. This lab puts the lessons' 24 files into the repository unchanged and adds northdesk/estimate.py, a thin estimator that only imports them.

The estimator reproduces the roadmap's worked estimate end to end, then Northdesk's own numbers from the shared data. It writes docs/numbers.md, which nobody edits by hand. One decision follows from the arithmetic, and it gets the course's first architecture decision record. No cell calls a hosted model, so you need no key.

Open a new Colab notebook, call it module-03-lab.ipynb, and run each cell in order.