Pin remaining deepcopy and copy.copy paths for pickle-guard classes

The __reduce__ raise should already cover all three operations
(pickle.dumps, copy.copy, copy.deepcopy — the latter two route
through __reduce_ex__(2) which delegates to __reduce__). Only
DqliteConnection / ConnectionPool had the full three-way matrix
pinned; ClusterClient was missing deepcopy and DqliteProtocol was
missing both copy.copy and copy.deepcopy.

Pin the gaps so a future "raise from __reduce_ex__ only on
protocol >= 2" regression or a custom __copy__ / __deepcopy__
accidentally added to one of these classes is caught.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: antoineleclair

tests/test_pickle_guards.py

@@ -76,6 +76,11 @@ def test_copy_copy_raises(self) -> None:
         with pytest.raises(TypeError, match="ClusterClient"):
             copy.copy(cluster)
 
+    def test_copy_deepcopy_raises(self) -> None:
+        cluster = ClusterClient(node_store=MemoryNodeStore(["localhost:9001"]))
+        with pytest.raises(TypeError, match="ClusterClient"):
+            copy.deepcopy(cluster)
+
 
 class TestDqliteProtocolPickleGuard:
     def test_pickle_raises(self) -> None:
@@ -89,3 +94,27 @@ def test_pickle_raises(self) -> None:
         proto = DqliteProtocol(reader=reader, writer=writer)
         with pytest.raises(TypeError, match="DqliteProtocol"):
             pickle.dumps(proto)
+
+    def test_copy_copy_raises(self) -> None:
+        import asyncio
+        from unittest.mock import MagicMock
+
+        from dqliteclient.protocol import DqliteProtocol
+
+        reader = MagicMock(spec=asyncio.StreamReader)
+        writer = MagicMock(spec=asyncio.StreamWriter)
+        proto = DqliteProtocol(reader=reader, writer=writer)
+        with pytest.raises(TypeError, match="DqliteProtocol"):
+            copy.copy(proto)
+
+    def test_copy_deepcopy_raises(self) -> None:
+        import asyncio
+        from unittest.mock import MagicMock
+
+        from dqliteclient.protocol import DqliteProtocol
+
+        reader = MagicMock(spec=asyncio.StreamReader)
+        writer = MagicMock(spec=asyncio.StreamWriter)
+        proto = DqliteProtocol(reader=reader, writer=writer)
+        with pytest.raises(TypeError, match="DqliteProtocol"):
+            copy.deepcopy(proto)