feat: add NodeRole enum (VOTER, STANDBY, SPARE)

Adds NodeRole(IntEnum) to constants.py matching Go's protocol.Voter/
StandBy/Spare and C's DQLITE_VOTER/DQLITE_STANDBY/DQLITE_SPARE.
Exported from the top-level package. Users no longer need to hardcode
magic numbers for cluster role values.

Closes #127

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitewire/__init__.py

@@ -49,6 +49,7 @@
     ROW_DONE_MARKER,
     ROW_PART_BYTE,
     ROW_PART_MARKER,
+    NodeRole,
     RequestType,
     ResponseType,
     ValueType,
@@ -60,6 +61,7 @@
     "EncodeError",
     "MessageDecoder",
     "MessageEncoder",
+    "NodeRole",
     "PROTOCOL_VERSION",
     "PROTOCOL_VERSION_LEGACY",
     "ProtocolError",

src/dqlitewire/constants.py

@@ -74,3 +74,15 @@ class ValueType(IntEnum):
     UNIXTIME = 9  # Unix time (deprecated, maps to INTEGER)
     ISO8601 = 10  # ISO8601 string (maps to TEXT)
     BOOLEAN = 11  # Boolean (maps to INTEGER)
+
+
+class NodeRole(IntEnum):
+    """Node roles in a dqlite cluster.
+
+    Matches Go's protocol.Voter/StandBy/Spare and C's
+    DQLITE_VOTER/DQLITE_STANDBY/DQLITE_SPARE.
+    """
+
+    VOTER = 0
+    STANDBY = 1
+    SPARE = 2

tests/test_constants.py

@@ -133,6 +133,30 @@ def test_nodeinfo_importable_from_messages(self) -> None:
         assert NodeInfo is DirectNodeInfo
 
 
+class TestNodeRoleValues:
+    """Verify NodeRole enum matches Go's protocol constants."""
+
+    def test_voter_is_0(self) -> None:
+        from dqlitewire.constants import NodeRole
+
+        assert NodeRole.VOTER == 0
+
+    def test_standby_is_1(self) -> None:
+        from dqlitewire.constants import NodeRole
+
+        assert NodeRole.STANDBY == 1
+
+    def test_spare_is_2(self) -> None:
+        from dqlitewire.constants import NodeRole
+
+        assert NodeRole.SPARE == 2
+
+    def test_importable_from_top_level(self) -> None:
+        from dqlitewire import NodeRole
+
+        assert NodeRole.VOTER == 0
+
+
 class TestTypeDictCompleteness:
     """Verify REQUEST_TYPES and RESPONSE_TYPES cover all enum members."""