zarr-metadata: Scope.update() replaces slots whole; adding a definition can silently drop the defaults #424

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Scope.update() replaces each slot whole: passing data_types=[NEW_DEFINITION] silently drops every default data type from the scope rather than adding one. Extending the default scope requires re-splicing the defaults by hand:

GEOZARR_SCOPE = CORE_AND_EXTENSIONS.update(
    data_types=[
        *CORE_AND_EXTENSIONS.data_types.values(),
        FIXED_LENGTH_UTF32,
        NULL_TERMINATED_BYTES,
    ],
)

Encountered while extending CORE_AND_EXTENSIONS for GeoZarr validation in EOPF-Explorer/data-model#330. The failure mode of getting it wrong is nasty for exactly this API's audience: with strict validation on, a scope that silently lost its defaults blames every ordinary document for "unclaimed" core names, and the error points at the store, not at the scope construction.

The ask: an additive operation — scope.extend(data_types=[...]), or merge semantics on update — so adding a definition cannot drop the existing ones. If update's replace-whole semantics are intentional, a note in its docstring showing the splice idiom would at least make the footgun visible.