feat(client-python): add write_array_elements default-fill helper and document semantics

Regenerate Python proto bindings to pick up MxSparseArray/MxSparseElement/
sparse_array_value from the shared mxaccess_gateway.proto. Add
Session.write_array_elements which builds an MxValue(sparse_array_value=…)
from a {index→scalar} dict and delegates to the existing write(). Add 8 pytest
tests covering builder correctness and full round-trip wire shape. Update
README with a default-fill semantics paragraph and bare-name array-write note.

clients/python/src/zb_mom_ww_mxgateway/generated/galaxy_repository_pb2.py

@@ -2,7 +2,7 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # NO CHECKED-IN PROTOBUF GENCODE
 # source: galaxy_repository.proto
-# Protobuf Python Version: 6.31.1
+# Protobuf Python Version: 6.33.5
 """Generated protocol buffer code."""
 from google.protobuf import descriptor as _descriptor
 from google.protobuf import descriptor_pool as _descriptor_pool
@@ -12,8 +12,8 @@ from google.protobuf.internal import builder as _builder
 _runtime_version.ValidateProtobufRuntimeVersion(
     _runtime_version.Domain.PUBLIC,
     6,
-    31,
-    1,
+    33,
+    5,
     '',
     'galaxy_repository.proto'
 )

clients/python/src/zb_mom_ww_mxgateway/generated/galaxy_repository_pb2_grpc.py

@@ -5,7 +5,7 @@ import warnings
 
 import galaxy_repository_pb2 as galaxy__repository__pb2
 
-GRPC_GENERATED_VERSION = '1.80.0'
+GRPC_GENERATED_VERSION = '1.81.1'
 GRPC_VERSION = grpc.__version__
 _version_not_supported = False
 
@@ -25,7 +25,7 @@ if _version_not_supported:
     )
 
 
-class GalaxyRepositoryStub(object):
+class GalaxyRepositoryStub:
     """Wire-compatibility policy (ProtobufStyleGuide): this contract evolves
     additively only. Never renumber or repurpose an existing field number or
     enum value. When a field or enum value is removed, add a `reserved` range
@@ -72,7 +72,7 @@ class GalaxyRepositoryStub(object):
                 _registered_method=True)
 
 
-class GalaxyRepositoryServicer(object):
+class GalaxyRepositoryServicer:
     """Wire-compatibility policy (ProtobufStyleGuide): this contract evolves
     additively only. Never renumber or repurpose an existing field number or
     enum value. When a field or enum value is removed, add a `reserved` range
@@ -162,7 +162,7 @@ def add_GalaxyRepositoryServicer_to_server(servicer, server):
 
 
  # This class is part of an EXPERIMENTAL API.
-class GalaxyRepository(object):
+class GalaxyRepository:
     """Wire-compatibility policy (ProtobufStyleGuide): this contract evolves
     additively only. Never renumber or repurpose an existing field number or
     enum value. When a field or enum value is removed, add a `reserved` range

clients/python/src/zb_mom_ww_mxgateway/generated/mxaccess_gateway_pb2_grpc.py

@@ -5,7 +5,7 @@ import warnings
 
 import mxaccess_gateway_pb2 as mxaccess__gateway__pb2
 
-GRPC_GENERATED_VERSION = '1.80.0'
+GRPC_GENERATED_VERSION = '1.81.1'
 GRPC_VERSION = grpc.__version__
 _version_not_supported = False
 
@@ -25,7 +25,7 @@ if _version_not_supported:
     )
 
 
-class MxAccessGatewayStub(object):
+class MxAccessGatewayStub:
     """Wire-compatibility policy (ProtobufStyleGuide): this contract evolves
     additively only. Never renumber or repurpose an existing field number or
     enum value. When a field or enum value is removed, add a `reserved` range
@@ -78,7 +78,7 @@ class MxAccessGatewayStub(object):
                 _registered_method=True)
 
 
-class MxAccessGatewayServicer(object):
+class MxAccessGatewayServicer:
     """Wire-compatibility policy (ProtobufStyleGuide): this contract evolves
     additively only. Never renumber or repurpose an existing field number or
     enum value. When a field or enum value is removed, add a `reserved` range
@@ -189,7 +189,7 @@ def add_MxAccessGatewayServicer_to_server(servicer, server):
 
 
  # This class is part of an EXPERIMENTAL API.
-class MxAccessGateway(object):
+class MxAccessGateway:
     """Wire-compatibility policy (ProtobufStyleGuide): this contract evolves
     additively only. Never renumber or repurpose an existing field number or
     enum value. When a field or enum value is removed, add a `reserved` range

clients/python/src/zb_mom_ww_mxgateway/generated/mxaccess_worker_pb2.py

@@ -2,7 +2,7 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # NO CHECKED-IN PROTOBUF GENCODE
 # source: mxaccess_worker.proto
-# Protobuf Python Version: 6.31.1
+# Protobuf Python Version: 6.33.5
 """Generated protocol buffer code."""
 from google.protobuf import descriptor as _descriptor
 from google.protobuf import descriptor_pool as _descriptor_pool
@@ -12,8 +12,8 @@ from google.protobuf.internal import builder as _builder
 _runtime_version.ValidateProtobufRuntimeVersion(
     _runtime_version.Domain.PUBLIC,
     6,
-    31,
-    1,
+    33,
+    5,
     '',
     'mxaccess_worker.proto'
 )

clients/python/src/zb_mom_ww_mxgateway/generated/mxaccess_worker_pb2_grpc.py

@@ -4,7 +4,7 @@ import grpc
 import warnings
 
 
-GRPC_GENERATED_VERSION = '1.80.0'
+GRPC_GENERATED_VERSION = '1.81.1'
 GRPC_VERSION = grpc.__version__
 _version_not_supported = False
 

clients/python/src/zb_mom_ww_mxgateway/session.py

@@ -489,6 +489,56 @@ class Session:
             correlation_id=correlation_id,
         )
 
+    async def write_array_elements(
+        self,
+        server_handle: int,
+        item_handle: int,
+        element_data_type: "pb.MxDataType.ValueType",
+        total_length: int,
+        elements: dict[int, MxValueInput],
+        *,
+        user_id: int = 0,
+        correlation_id: str = "",
+    ) -> None:
+        """Write a partial array by specifying only the indices you want to set.
+
+        The gateway expands the sparse representation into a full ``total_length``
+        array before forwarding the write to MXAccess.  Indices not listed in
+        *elements* are filled with the type default for *element_data_type* (0,
+        False, empty string, Unix epoch for timestamps, etc.).  The previous
+        value at those positions is **not** preserved — this is a full array
+        replacement, not a patch.
+
+        Args:
+            server_handle: Handle returned by :meth:`register`.
+            item_handle: Handle returned by :meth:`add_item`.
+            element_data_type: ``pb.MX_DATA_TYPE_*`` enum value for the scalar
+                element type of the target array attribute.
+            total_length: Total number of elements in the written array.  Must
+                be > 0 and large enough to contain every index in *elements*.
+            elements: Mapping of zero-based element index to scalar value.
+                Values are converted with :func:`~zb_mom_ww_mxgateway.values.to_mx_value`.
+            user_id: Galaxy user id to stamp on the write (requires a prior
+                supervisory advise to take effect — see README).
+            correlation_id: Optional client-supplied correlation token echoed
+                in the command reply.
+        """
+        sparse = pb.MxSparseArray(
+            element_data_type=element_data_type,
+            total_length=total_length,
+            elements=[
+                pb.MxSparseElement(index=idx, value=to_mx_value(val))
+                for idx, val in elements.items()
+            ],
+        )
+        await self.write(
+            server_handle,
+            item_handle,
+            pb.MxValue(sparse_array_value=sparse),
+            user_id=user_id,
+            correlation_id=correlation_id,
+        )
+
     async def write2(
         self,
         server_handle: int,