clawhdf5: FileEditor reports filters it cannot run as Error::Unsupported

A dataset whose filter this build cannot encode (scale-offset, N-Bit, SZIP;
a plugin filter the build lacks) failed with Error::Format("unsupported
filter: 6"), although the editor documents every refused edit as
Error::Unsupported, and the Python bindings raised ValueError rather than
NotImplementedError. Every edit now maps FormatError::UnsupportedFilter to
Error::Unsupported; the file is left untouched as before.

Test: edit_interop unencodable_filters_are_unsupported — h5py scale-offset
datasets (integer with chunks, integer never written, float D-scale):
Error::Unsupported naming the filter, and the file byte for byte unchanged.
Fails on the previous editor (Format(UnsupportedFilter(6))).

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

CHANGELOG.md

@@ -40,8 +40,10 @@
     (`Error::Unsupported`, file untouched) when any part is not supported:
     new chunks in a version-2 B-tree index (two or more unlimited
     dimensions) or an implicit index, shrinking, variable-length and
-    reference data, attributes in dense storage, past an object's compact
-    limit or with tracked creation order, files with a metadata cache
+    reference data, chunks through a filter this build cannot encode
+    (scale-offset, N-Bit, SZIP), attributes in dense storage, past an
+    object's compact limit or with tracked creation order, files with a
+    metadata cache
     image, paged or persistent free space, or marked open by another
     writer. New error variants `Error::Unsupported`,
     `Error::InvalidArgument`, `Error::Locked`, and `clawhdf5::Error` is now