py: boolean-mask keys raise NotImplementedError, not TypeError

h5py supports boolean masks for reads and writes; clawhdf5 supports
neither, so a mask is an unsupported operation (NotImplementedError, as
for every other edit the bindings cannot do), not an invalid key.

Tests: test_unsupported_edits_are_clear_errors (1-D, N-D and per-axis
mask writes, file unchanged) and test_boolean_masks_are_refused (reads).

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

crates/clawhdf5-py/README.md

@@ -43,8 +43,9 @@ with clawhdf5.File("data.h5", "r") as f:
   Other types raise `TypeError`.
 - Keys are h5py's: integers, slices with a positive step, `...`, one
   increasing list of integers, compound field names. Each maps onto a
-  hyperslab selection. `None`, negative steps and boolean masks are refused
-  with h5py's errors.
+  hyperslab selection. `None` and negative steps are refused
+  with h5py's errors; boolean masks (which h5py supports) raise
+  `NotImplementedError`, for reads and writes.
 - What is read from the file: a selection whose bounding box covers at
   most half the dataset decodes only the chunks (or contiguous rows) the box
   overlaps. The library decodes the whole dataset for a larger box