Compatible null annotations

When annotating optional or nullable types in Python, ensure compatibility across all supported Python versions. For codebases supporting Python 3.9:

1. Add from __future__ import annotations at the top of files using the union type syntax:

   from __future__ import annotations
      
   class ExInfo:
       name: str
       retry: bool
       description: str | None
   

2. Alternatively, use typing.Optional[X] instead of X | None syntax:

   import typing
      
   class CoderPrompts:
       repo_content_prefix: typing.Optional[str] = """Here are summaries..."""
   

This ensures proper null handling with type annotations while maintaining backward compatibility with Python 3.9, preventing runtime errors like TypeError: unsupported operand type(s) for |: 'type' and 'NoneType'.