Zarr float64

[fcollman]

this adds float64 support to zarr via downcasting like nifti.. addresses #875 following along the pattern established with #849

[fcollman]

I have tested this using this snippet test to create a 64 bit float zarr and serve it to this branch

# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "zarr",
#     "numpy",
#     "neuroglancer",
# ]
# ///
import pathlib
import shutil
import time


import numpy as np
import zarr

import neuroglancer.static_file_server

# Ensure we start with a clean directory for the tutorial
script_dir = pathlib.Path(__file__).resolve().parent
datadir = script_dir / ".." / "data" / "zarr-tutorial"
datadir = datadir.resolve()
if datadir.exists():
    shutil.rmtree(datadir)
datadir.mkdir(parents=True, exist_ok=True)

output = datadir / "test.zarr"
z = zarr.create_array(shape=(40, 50, 50), chunks=(10, 10, 10), dtype="f8", store=output, compressors=None)
z[:] = np.random.rand(40, 50, 50)

# Serve ../data on localhost for Neuroglancer
data_dir = script_dir / ".." / "data"
data_dir = data_dir.resolve()
server = neuroglancer.static_file_server.StaticFileServer(
    str(data_dir), bind_address="127.0.0.1", daemon=True
)

print(f"Data directory served at: {server.url}")

print("Press Ctrl+C to stop the server.")
try:
    while True:
        time.sleep(1)
except KeyboardInterrupt:
    pass

[fcollman]

this is not functioning properly.. need to go back to drawing board.