Fix ruff lint: remove unused imports (ctypes, PayloadType)

Unused after OutputType/PayloadType split and think() dedup refactor.

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

Author: SStas

src/avp/connectors/llamacpp.py

@@ -224,8 +224,6 @@ def think(
         Returns:
             AVPContext containing the enriched hidden state and live context.
         """
-        import ctypes
-
         import numpy as np
         from llama_cpp import llama_cpp as lc
 

src/avp/context.py

@@ -77,7 +77,6 @@ def to_bytes(
             AVPMetadata,
             CommunicationMode,
             DataType,
-            PayloadType,
         )
         from .codec import encode_kv_cache
         from .kv_cache import serialize_kv_cache

src/avp/easy.py

@@ -37,7 +37,7 @@
     from .results import InspectResult
 
 from .results import GenerateResult, ThinkResult
-from .types import OutputType, PayloadType
+from .types import OutputType
 
 logger = logging.getLogger(__name__)