refactor(types): Phase 4 type hint sweep — core modules

gemini.py

@@ -1,11 +1,13 @@
 # gemini.py
+from __future__ import annotations
 import tomllib
 from pathlib import Path
+from typing import Any
 from google import genai
 from google.genai import types
 
-_client = None
-_chat = None
+_client: genai.Client | None = None
+_chat: Any = None
 
 def _load_key() -> str:
  with open("credentials.toml", "rb") as f: