Integration test: full foundation stack wiring

The key challenge in this integration test is isolating Flutter's WidgetsBinding while still testing real provider wiring. Use TestWidgetsFlutterBinding (automatically set by flutter_test) and create a FakeAccessibilityFeatures helper that allows toggling screen reader state in tests. For Supabase, inject a FakeSupabaseClient that returns empty streams and no-op operations. For ScreenReaderDetectionService, the service should be wired through its Riverpod provider so the test verifies the actual provider graph, not just the service in isolation.

The integration test should be the single authoritative test confirming 'all five components work together correctly', forming a regression baseline for future epics that build on this foundation.

Use flutter_test with testWidgets() for widget-mounted integration tests. Create a TestApp widget that wraps content in ProviderScope with the real provider graph (no overrides except WidgetsBinding and Supabase). Use a ProviderObserver to detect any unhandled provider errors during the test. For stream assertions, use tester.pump() to advance the frame and then read the provider's current value using ProviderContainer.read().

For wiring verification, use ProviderContainer.listen() to subscribe to each provider's stream and assert at least one emission. For the SemanticsWrapperWidget wiring test, use tester.ensureSemantics() and assert semantics node presence/absence based on screen reader state changes. Organise tests as individual testWidgets() blocks, one per foundation component, plus one end-to-end wiring test.