Expr.shrink_dtype() breaks broadcasting

[guyrosin]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

import polars as pl

pl.DataFrame({"a":[1,2], "b":[3,4]}).with_columns(pl.lit(5))  # OK
pl.DataFrame({"a":[1,2], "b":[3,4]}).with_columns(pl.lit(5).shrink_dtype().first())  # OK

pl.DataFrame({"a":[1,2], "b":[3,4]}).with_columns(pl.lit(5).shrink_dtype())  # InvalidOperationError

Log output

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/ubuntu/playground/.venv/lib/python3.11/site-packages/polars/dataframe/frame.py", line 9141, in with_columns
    return self.lazy().with_columns(*exprs, **named_exprs).collect(_eager=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ubuntu/playground/.venv/lib/python3.11/site-packages/polars/lazyframe/frame.py", line 2032, in collect
    return wrap_df(ldf.collect(callback))
                   ^^^^^^^^^^^^^^^^^^^^^
polars.exceptions.InvalidOperationError: Series literal, length 1 doesn't match the DataFrame height of 2

If you want this Series to be broadcasted, ensure it is a scalar (for instance by adding '.first()').

Issue description

Broadcasting a literal doesn't work after calling shrink_dtype().
The error message is helpful and explains the problem, but I find it nonintuitive - shrink_dtype() should just shrink the type, nothing more :)

Expected behavior

I expected the shrunk literal to be broadcasted.

Installed versions

pl.show_versions()
--------Version info---------
Polars:              1.7.1
Index type:          UInt32
Platform:            Linux-6.5.0-1024-aws-x86_64-with-glibc2.35
Python:              3.11.9 (main, Jul 13 2024, 23:44:43) [Clang 17.0.6 ]

----Optional dependencies----
adbc_driver_manager  <not installed>
altair               5.4.1
cloudpickle          3.0.0
connectorx           <not installed>
deltalake            <not installed>
fastexcel            0.11.6
fsspec               2024.9.0
gevent               <not installed>
great_tables         <not installed>
matplotlib           3.9.2
nest_asyncio         1.6.0


numpy                1.26.4
openpyxl             <not installed>
pandas               2.2.2
pyarrow              17.0.0
pydantic             2.9.1
pyiceberg            <not installed>
sqlalchemy           2.0.34
torch                2.2.2+cu121
xlsx2csv             0.8.3
xlsxwriter           <not installed>