Add Redis scan_keys iterator API.

Provide a SCAN-based key iterator for Redis adapters so callers can enumerate large keyspaces without relying on blocking KEYS lookups.

Co-authored-by: Cursor <[email protected]>

tests/unit/redis_adapter_test.py

@@ -114,3 +114,53 @@ def test_connect_closes_existing_non_injected_client(
 
     stale_client.close.assert_called_once()
     assert adapter._client is new_client
+
+
+def test_scan_keys_yields_decoded_keys() -> None:
+    mock_client = MagicMock(spec=redis.Redis)
+    mock_client.scan_iter.return_value = iter([b"key1", b"key2"])
+    adapter = RedisAdapter(config=TEST_REDIS_CONFIG, client=mock_client)
+
+    keys = list(adapter.scan_keys("key*"))
+
+    assert keys == ["key1", "key2"]
+    mock_client.scan_iter.assert_called_once_with(match="key*")
+    mock_client.keys.assert_not_called()
+
+
+def test_scan_keys_forwards_count() -> None:
+    mock_client = MagicMock(spec=redis.Redis)
+    mock_client.scan_iter.return_value = iter([b"key1"])
+    adapter = RedisAdapter(config=TEST_REDIS_CONFIG, client=mock_client)
+
+    keys = list(adapter.scan_keys("key*", count=50))
+
+    assert keys == ["key1"]
+    mock_client.scan_iter.assert_called_once_with(match="key*", count=50)
+
+
+def test_list_keys_raises_value_error_on_invalid_pattern() -> None:
+    mock_client = MagicMock(spec=redis.Redis)
+    adapter = RedisAdapter(config=TEST_REDIS_CONFIG, client=mock_client)
+
+    invalid_patterns = ["", 123, None]
+    for pattern in invalid_patterns:
+        with pytest.raises(ValueError, match="Pattern must be a non-empty string"):
+            adapter.list_keys(pattern)  # type: ignore[arg-type]
+
+
+def test_scan_keys_raises_value_error_on_invalid_pattern() -> None:
+    mock_client = MagicMock(spec=redis.Redis)
+    adapter = RedisAdapter(config=TEST_REDIS_CONFIG, client=mock_client)
+
+    invalid_patterns = ["", 123, None]
+    for pattern in invalid_patterns:
+        with pytest.raises(ValueError, match="Pattern must be a non-empty string"):
+            list(adapter.scan_keys(pattern))  # type: ignore[arg-type]
+
+
+def test_scan_keys_raises_connection_error_when_not_connected() -> None:
+    adapter = RedisAdapter(config=TEST_REDIS_CONFIG)
+
+    with pytest.raises(ConnectionError):
+        list(adapter.scan_keys("key*"))