some ew4 tutorial fixes (#263)

* added nc4 as a file extension, and added a check to zarr index so that fsspec urls for remote zarr archives are not turned into pathlib objects (and thus become invalid)

* added a zarr loading demo to complement the bug fix.

AI Usage Summary: nil AI was used

Author: stevehadd

docs/notebooks/Gallery.ipynb

@@ -132,7 +132,8 @@
     "| Multi-sample (multi-file) retrieval | -- | [Complex Time Series Retrieval](./data/GettingComplexSeries.ipynb) | 18 Aug 2025 |\n",
     "| Transform-on-load | How to transform and adjust data at load-time | [Using Built-In Operations](./data/UsingTheInBuiltOperations.ipynb) | 18 Aug 2025 |\n",
     "| Applying data transforms | -- | [Applying Data Transforms](./data/Transforms.ipynb) | 18 Aug 2025 |\n",
-    "| Geospatial subsetting | -- | [Region Cutting](./data/RegionCutting.ipynb) | 18 Aug 2025 |\n"
+    "| Geospatial subsetting | -- | [Region Cutting](./data/RegionCutting.ipynb) | 18 Aug 2025 |\n",
+    "| Remote Zarr Loading | Demontsrates loading data in a remote zarr archive | [Remote Zarr Loading](./data/Zarr_  |2 June 2026 |\n"
    ]
   },
   {
@@ -170,7 +171,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.13.9"
+   "version": "3.14.5"
   }
  },
  "nbformat": 4,