fix: resolve audited dispatch, kernel, and rollout bugs

- re-register the linear family with the operator dispatcher (ASTR_OPS / op_backend / resolve)
- fix bf16 gemv misaligned-address faults and element mispairing for offset weights
- reject misaligned bf16_swiglu inputs with a clear error and fall back in the backend gate
- make the rollout reuse decision, validation, and return atomic under one policy snapshot
- add the documented post-scoring rollout version check
- derive live+1 under the scheduler lock in optimizer_step via apply_weight_update(None, ...)
- reject rollout_max_policy_lag below rollout_interval - 1 at config time
- sync gemv stream-test inputs before switching streams; drop dead loader imports

astrai/config/train_config.py

@@ -234,4 +234,15 @@ class TrainConfig(BaseConfig):
                     f"numbers of forward passes and desynchronize the "
                     f"ddp/fsdp collectives, deadlocking NCCL"
                 )
+            if (
+                self.rollout_max_policy_lag is not None
+                and self.rollout_max_policy_lag < self.rollout_interval - 1
+            ):
+                raise ValueError(
+                    f"rollout_max_policy_lag={self.rollout_max_policy_lag} "
+                    f"cannot be below rollout_interval - 1 = "
+                    f"{self.rollout_interval - 1}: the replay cache reuses "
+                    f"rollouts up to that lag, so a tighter bound guarantees "
+                    f"a fatal RolloutVersionError mid-training"
+                )
         return self