v0.2.0 of vehicle_condition_fusion

Safety-calibrated fusion of in-vehicle signals (road friction, TCS/ABS, wiper/rain, ambient temperature) into a driving-condition hazard verdict, with an honest-degradation rail. Pure Dart, no Flutter [...] Changelog excerpt: - **Lower the floor — try it with just a laptop.**Added an opt-in scenarios.dartlibrary (a SEPARATE import, intentionally NOT in the main barrel, so the safety-calibrated fusion is untouched) with: - replayWinterDrive(frames, {step})— replays a list of VehicleConditionSignalsas a stream (partial-frame style, to pair with VehicleConditionFusion.fromPartialFrames); step: Duration.zero(default) is instant for tests, a non-zero step paces a live demo. - named **ILLUSTRATIVE / SYNTHETIC[...]