Prove transit app empty state before delivery

Continue the existing transit timetable explorer from the latest partial run. The application already appears to show an empty state, but delivery was refused because the final acceptance evidence did not retain a real browser observation of it. Keep the current application and tests unless a defect is found. Add a focused automated regression that proves the empty state after typing an unmatched stop. Before final delivery, use validate_html on the final files at 390px: select a route, type a nonexistent stop, and assert #empty-state is visible, contains 'No departures found', and there are zero .departure-card elements; record the interaction and result. Also verify the existing keyboard and desktop behavior on the final files. Read back modified files. Do not hand-edit .atoma-probes.json; use record_probe for execution evidence. Publish only after the browser proof and tests are visible to the final acceptance judge.