AttributeError when using as_loaded_data with datasets argument

It seems that `as_loaded_data` in `finder.py` has an AttributeError when calling it with the `datasets` argument (datasets='gain' or datasets='vis').

Code Ex.:
`visst = res_corr[0].as_loaded_data(freq_sel=np.arange(236,492),datasets='gain')`

Error:
```
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
Cell In[12], line 1
----> 1 visst = res_corr[0].as_loaded_data(freq_sel=np.arange(236,492),datasets='gain')

File ~/chime/venv/lib/python3.13/site-packages/ch_util/finder.py:1607, in CorrDataInterval.as_loaded_data(self, prod_sel, freq_sel, datasets)
1589 def as_loaded_data(self, prod_sel=None, freq_sel=None, datasets=None):
1590 """Load data interval to memory as an :class:`andata.CorrData` instance
1591
1592 Parameters
(...)
1605
1606 """
-> 1607 return super().as_loaded_data(
1608 prod_sel=prod_sel, freq_sel=freq_sel, datasets=datasets
1609 )

File ~/chime/venv/lib/python3.13/site-packages/ch_util/finder.py:1575, in BaseDataInterval.as_loaded_data(self, **kwargs)
1573 for k, v in kwargs.items():
1574 if v is not None:
-> 1575 setattr(reader, k, v)
1576 return reader.read()

AttributeError: property 'datasets' of 'CorrReader' object has no setter
```

Start in finder.py at BaseDataInterval.as_loaded_data and CorrDataInterval.as_loaded_data, then inspect how CorrReader exposes the datasets property. Reproduce the reported as_loaded_data call with datasets='gain' and datasets='vis'; done means both selections load without the CorrReader setter AttributeError.

Written by the indexing model from the issue text.