Standalone net9.0 xUnit project at tests/FieldLogger.Tests (no MAUI workload)
so `dotnet test` runs fast in the QA gate. Smoke suite only for now; real app
logic tests land once codec/sim are factored into a workload-free library.
Trace: SRS §6 gate, NFR-8.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
