GenCast autoregressive rollout fails with JaxArrayWrapper / DynamicJaxprTracer __array_ufunc__ TypeError on both GPU and Colab TPU

Hi, would really appreciate some help with the following issue of getting a TypeError while running the GenCast autoregressive rollout. It fails with a TypeError related to xarray_jax.JaxArrayWrapper interacting with a DynamicJaxprTracer.

The failure occurs during the autoregressive rollout step `(chunked_prediction_generator_multiple_runs)` in the GenCast demo.

I can reproduce the same error on a local multi-GPU machine, and on Google Colab TPU (v5e-1 TPU with 2025.07 runtime version), and I think the error is related to the GenCast rollout path interacting with xarray_jax.

The simpler GraphCast forward pass works correctly.

Execution fails with:

```
TypeError: operand type(s) all returned NotImplemented from __array_ufunc__(
, '__call__',
JitTracer(float32[]),
xarray_jax.JaxArrayWrapper(JitTracer(float32[1,1,181,360]))
): 'DynamicJaxprTracer', 'JaxArrayWrapper'
```

For reproduction:
Using GenCast demo notebook, the failure occurs in the Autoregressive rollout cell:
```
chunks = []
for chunk in rollout.chunked_prediction_generator_multiple_runs(
predictor_fn=run_forward_pmap,
rngs=rngs,
inputs=eval_inputs,
targets_template=eval_targets * np.nan,
forcings=eval_forcings,
num_steps_per_chunk=1,
num_samples=num_ensemble_members,
pmap_devices=jax.local_devices(),
):
chunks.append(chunk)

predictions = xarray.combine_by_coords(chunks)
```
Setup:

Machine:

Linux cluster

2× NVIDIA GPUs
Python environment:
```
Python 3.11
jax 0.4.38
jaxlib 0.4.38
numpy 2.4.2
xarray 2024.11.0
pandas 2.2.3
```
Devices detected:
```
devices: [CudaDevice(id=0), CudaDevice(id=1)]
backend: gpu
```
Error traceback ends with:
```
TypeError: operand type(s) all returned NotImplemented from __array_ufunc__(
, '__call__',
JitTracer(float32[]),
xarray_jax.JaxArrayWrapper(JitTracer(float32[1,1,181,360]))
)
```

Start with the GenCast demo notebook's autoregressive rollout cell and reproduce the failure using chunked_prediction_generator_multiple_runs on the listed GPU or TPU setup. Compare it with the working GraphCast forward pass and trace the interaction between the rollout inputs and xarray_jax wrappers. Done means the GenCast autoregressive rollout completes without the DynamicJaxprTracer __array_ufunc__ TypeError.

Written by the indexing model from the issue text.