Add type ignore for Redis keys method in strict mode

Add type: ignore comments to handle Redis keys() method's partial
type information in pyright strict mode while preserving type safety
with cast annotations.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: chrisguidry

tests/test_docket.py

@@ -1,4 +1,5 @@
 from datetime import datetime, timedelta, timezone
+from typing import cast
 from unittest.mock import AsyncMock
 
 import pytest
@@ -150,15 +151,17 @@ async def test_clear_no_redis_key_leaks(docket: Docket, the_task: AsyncMock):
     await docket.add(the_task, when=future + timedelta(seconds=1))("scheduled2")
 
     async with docket.redis() as r:
-        keys_before = len(await r.keys("*"))  # type: ignore
+        keys_before = cast(list[str], await r.keys("*"))  # type: ignore
+        keys_before_count = len(keys_before)
 
     result = await docket.clear()
     assert result == 5
 
     async with docket.redis() as r:
-        keys_after = len(await r.keys("*"))  # type: ignore
+        keys_after = cast(list[str], await r.keys("*"))  # type: ignore
+        keys_after_count = len(keys_after)
 
-    assert keys_after <= keys_before
+    assert keys_after_count <= keys_before_count
 
     snapshot = await docket.snapshot()
     assert len(snapshot.future) == 0