- Add PostHog feature flag support to TelemetryService
- Implement default mode experiment (architect vs code)
- Add feature flag checking to PostHogTelemetryClient
- Initialize default mode based on feature flag for new users
- Add tests for mode selection logic
- Add documentation for the experiment
The feature flag "default-mode-experiment" controls whether new users
see "code" or "architect" as their default mode. Existing users are
not affected.
