Prototype — The Front End, Before the Backend

The plan says what gets built, designer says how it looks, and the plan's use cases say what each screen does. This skill turns the three into an app the founder can use — in the real stack, with no server behind it.

The frontend is finished; the backend is absent. Buttons act, forms save, lists change, guards redirect — all against fixture data held in the browser, reset when the tab closes. No database, no auth provider, no network.

Nothing in the app may announce that it is a prototype. No badge, no banner, no index of screens, no "not implemented" note. A founder reviewing a demo reviews the demo; a founder using the product finds what is wrong with it. The honesty lives in PROTOTYPE.md, outside the app.

Screens are built in the real stack rather than mocked up, so the build fills them in later instead of replacing them. That is also what keeps this the cheap review: a screen change is still a markup change.