Add Microsoft.Extensions.DependencyInjection package and introduce an
IStartupTracer abstraction with NoOpStartupTracer (zero-overhead default)
and FileStartupTracer (renamed from WinUiStartupTrace). A StartupTracer
factory selects the implementation from environment configuration.
Consumers (App, MainWindow, MainWindowViewModel, SensorColumnMeasurer) now
depend on the non-nullable interface, removing null-conditional trace calls
and decoupling startup instrumentation from construction logic. No behavior
change: tracing still writes the same log when enabled.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Move the text-measurement cache, shared column-width state, 5-second settle timer, and persisted device-column width into a dedicated SensorColumnMeasurer service. MainWindow keeps the traced UpdateSensorColumnWidths wrapper and subscribes to a SettleTriggered event so tracing semantics are preserved.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
JMR-dev
