Finish the notes application

The final repository explains setup, route contracts, configuration, data lifetime, session behavior, test commands, and deployment limits. This is a small part of an Express 5 notes application with an HTML interface, a JSON API, sessions, tests, and production failure handling, but the boundary it creates affects everything that follows.

A finished Express app is not the number of routes; it is a request path you can reason about in success and failure. The useful target is not encyclopedic coverage. Make one deliberate choice, observe its consequences, and know which requirement would make you revise it.

Watch for one shortcut in particular: trying to add another feature while known failure paths and operating assumptions remain undocumented. It makes later failures harder to locate. Instead, run the complete test and deployment matrix, fix evidence-backed gaps, and publish the operational contract. Prefer an implementation you can explain from the outside before optimizing it.

Keep the wider goal in view: Ship the notes app with black-box tests, production controls, and a failure matrix that can be rerun after changes. A short observation with concrete evidence is more useful than a confident sentence with no reproduction path.

Hand the app to a clean environment and have another person start, test, use, stop, and diagnose it from the documentation. Hand the result to someone else and see whether the behavior is clear without an oral explanation.