AI SDK 7.0.85: image-gen billing fix, per-call image access

What shipped: Vercel released AI SDK ai@7.0.85 (plus the v6 line at 6.0.272) on August 30.

What changed:

Why a builder cares: If you route image generation through AI Gateway, this corrects a real cost-accounting bug on split requests — worth upgrading before you audit a bill. And if you build multi-image features, the new per-call access lets you track each generated image independently. Routine patch otherwise; no API breaks.