Improve error message of ome_zarr finder on read-only locations

[imagejan]

When you try running ome_zarr finder . in a directory with read-only permission, you currently get:

Traceback (most recent call last):
  File "/<user_path>/.pixi/envs/ome-zarr/bin/ome_zarr", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File "/<user_path>/.pixi/envs/ome-zarr/lib/python3.13/site-packages/ome_zarr/cli.py", line 210, in main
    ns.func(ns)
    ~~~~~~~^^^^
  File "/<user_path>/.pixi/envs/ome-zarr/lib/python3.13/site-packages/ome_zarr/cli.py", line 44, in finder
    bff_finder(args.path, args.port)
    ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
  File "/<user_path>/.pixi/envs/ome-zarr/lib/python3.13/site-packages/ome_zarr/utils.py", line 250, in finder
    with open(bff_csv, "w", newline="") as csvfile:
         ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
PermissionError: [Errno 13] Permission denied: './biofile_finder.csv'

I suggest wrapping these lines in a try .. catch clause:

ome-zarr-py/ome_zarr/utils.py

Lines 256 to 257 in 77e6d63

	with open(bff_csv, "w", newline="") as csvfile:
	writer = csv.writer(csvfile, delimiter=",")

.. and providing a more informative error message, such as:

'ome_zarr finder' needs write permission, the provided location {location} seems to be read-only.