[Bug]: A2A exceptions lost their structured __repr__ after the client error refactor (#761) #1347

What happened?

#683 (for #679) added structured __repr__ methods to the client exception classes. The client error refactor in #761 replaced those classes with the new A2AError-based hierarchy (src/a2a/utils/errors.py, src/a2a/client/errors.py), and the __repr__ methods were not carried over.

Exceptions now fall back to the default Exception.__repr__, which only wraps str() output and loses structured attributes. Since server and client errors share A2AError, this affects both sides:

>>> repr(AgentCardResolutionError('Failed to fetch agent card', status_code=404))
"AgentCardResolutionError('Failed to fetch agent card')"  # Loses status_code

>>> repr(InvalidParamsError('Invalid field', data={'field': 'id'}))
"InvalidParamsError('Invalid field')"  # Loses data

Suggested fix: add __repr__ to A2AError, so every domain and client error inherits it, and override it in AgentCardResolutionError, following the same pattern as #683:

# A2AError
def __repr__(self) -> str:
    return (
        f'{self.__class__.__name__}('
        f'message={self.message!r}, '
        f'data={self.data!r})'
    )

# AgentCardResolutionError
def __repr__(self) -> str:
    return (
        f'{self.__class__.__name__}('
        f'status_code={self.status_code!r}, '
        f'message={self.message!r})'
    )

This does not alter __str__ output, traceback formatting, exception hierarchy or catching behavior.

If dropping __repr__ in #761 was intentional, I may be missing some context. In that case, feel free to close this.

I have a fix ready and I'm opening a PR alongside this issue.

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