Test a Windows app

Four levels, cheapest first. Each new story gets the cheapest level that can prove its acceptance criteria. A bug fix starts with a test that fails.

Level	Proves	Speed
Unit tests (xUnit)	Rules, parsing, data, the SQLite store	Seconds
Self-test (`--selftest`)	The app's real functions on a test store, every command has a shortcut	Seconds
UI Automation from outside (`scripts/uia.ps1`)	What Narrator reads, enabled states, buttons and rows that really work	Seconds
Debug bridge + computer use	Global shortcuts, tray, other apps, timing	Minutes

Snapshots (build-and-verify skill) prove how it looks. This skill proves how it behaves.

1. Unit tests

Logic lives in <App>.Core with no WinUI, so tests run without the app.