feat: version rollout weight updates

Track a monotonic policy version across optimizer steps, scheduler updates, and rollout results. Serialize synchronous generation with weight acknowledgements and invalidate reusable prefix KV entries so cached samples remain attributable to the behavior policy that generated them.

astrai/inference/cache/pool.py

@@ -338,6 +338,14 @@ class TaskCacheManager:
         if state is not None:
             self._strategy.record_hashes(state, prompt_ids, start_logical_page)
 
+    def invalidate_cache(self) -> int:
+        """Drop reusable KV entries once all task-owned entries are released."""
+        if self._states:
+            raise RuntimeError("Cannot invalidate KV cache while tasks are active")
+        self._bind_state = None
+        self._bind_was_steady = False
+        return self._strategy.invalidate_cache()
+
     @staticmethod
     def task_cacheable_ids(task_id: str, prompt_ids: List[int], output_ids: List[int]):
         return list(prompt_ids) + list(output_ids[:-1])