## Problem

The Akto guardrail integration currently only supports pre-call and post-call hooks. Three gaps: 1. No `during_call` mode — cannot inspect streaming chunks as they arrive 2. No end-of-stream accumulation mode for streaming — post-call fires before the full response is assembled 3. Model-group scoping is absent — Akto checks fire on every model regardless of which model group the request targets

## Proposed fix

Add `during_call` hook support to the Akto guardrail. Add an end-of-stream accumulation mode that buffers streaming chunks and fires the Akto check once the stream completes. Add a `model_group` scoping field so Akto checks can be restricted to specific model groups.

## Files

- `litellm/integrations/` (Akto guardrail implementation)