agent-platform release v4.89.0

spec.router.scheduler: a serving preset switches the llm-d endpoint picker for itself (giantswarm/agent-platform#507; epic giantswarm/giantswarm#37639). model-manager composes an LLMInferenceService without the picker unless the backend document’s spec.kserve.router.scheduler says otherwise, and reads a preset’s own spec.router.scheduler (true or false) over it. The preset schema now admits spec.router with scheduler alone, and the render refuses any other key under spec.router and a non-boolean scheduler, naming the preset. A preset that switches the picker on needs the Gateway API Inference Extension on the models Gateway (#504). No shipped preset sets it; the default render is unchanged. make verify-serving-slice publishes a values preset with router.scheduler: true unchanged and fails the render on the other shapes.