Unable to run groupby, map after shuffle_to_chunks

What happened?

ValueError: Array chunk size or shape is unknown. Possible solution with x.compute_chunk_sizes()

What did you expect to happen?

Able to successfully iterate over groups and apply a function

Minimal Complete Verifiable Example

# /// script
# requires-python = ">=3.11"
# dependencies = [
#   "xarray[complete]@git+https://github.com/pydata/xarray.git@main",
# ]
# ///
#
# This script automatically imports the development branch of xarray to check for issues.
# Please delete this header if you have _not_ tested this script with `uv run`!

import xarray as xr
xr.show_versions()
import dask.array as da
import numpy as np
import xarray as xr

data = da.ones((583753, 184), chunks=(18243, 12))

y = np.random.choice(np.array([1, 2, 3, 4, 5]), size=data.shape[0], replace=True)
d = xr.DataArray(data=data, coords={"y": y}, dims=["y", "x"])
d = d.groupby("y").shuffle_to_chunks()
d.data = d.data.compute_chunk_sizes()
d.groupby("y").map(lambda x: x)[
    0, 0].compute()  # ValueError: Array chunk size or shape is unknown. Possible solution with x.compute_chunk_sizes()

Steps to reproduce

No response

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.
• Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

Anything else we need to know?

No response

Environment

Run the provided MVCE and trace the groupby("y").shuffle_to_chunks() and subsequent groupby("y").map(...) entry points, focusing on where chunk sizes become unknown. Compare the data before and after compute_chunk_sizes(), then verify that iterating over groups and applying the identity function completes without the ValueError.