chore(ag-ui): add missing __future__ imports

Add missing `from __future__ import annotations` imports to ensure
ensure that only relevant type annotations are processed at runtime.

Fix incorrect import of `dataclass` in `args.py`.

Author: stevenh

examples/pydantic_ai_ag_ui_examples/api/agentic_generative_ui.py

@@ -1,5 +1,7 @@
 """Agentic Generative UI feature."""
 
+from __future__ import annotations
+
 from enum import StrEnum
 from typing import Annotated, Any, Literal
 

examples/pydantic_ai_ag_ui_examples/cli/__init__.py

@@ -1,5 +1,7 @@
 """Command line interface for the PydanticAI AG-UI servers."""
 
+from __future__ import annotations
+
 from .args import Args, parse_args
 
 __all__ = [

examples/pydantic_ai_ag_ui_examples/cli/args.py

@@ -1,12 +1,13 @@
 """CLI argument parser for the PydanticAI AG-UI servers."""
 
+from __future__ import annotations
+
 import argparse
+from dataclasses import dataclass
 from typing import Any
 
 from uvicorn.config import LOGGING_CONFIG
 
-from pydantic_ai.models import dataclass
-
 
 @dataclass
 class Args: