ac9dc02b51
Replace the nullable unique_ptr returned by CaptureFactory::create() with CaptureResult<std::unique_ptr<CaptureSession>> using the new CaptureError/CaptureResult pattern, mirroring codec/error.h. The stub now reports 'not implemented yet' as an error instead of returning nullptr. Update handoff memory with the review outcome and forward-looking notes for phases 3, 5, and 7.