[Bug]: v1.1.3 is unavailable on PyPI after publish workflow failure

Hi maintainers — thank you for the v1.1.3 release and for maintaining the Python SDK.

## What happened?

The GitHub release for v1.1.3 was published on August 18, but PyPI still reports v1.1.2 as the latest version and does not contain a `1.1.3` release. As a result, downstream projects cannot install the tagged release from PyPI (for example, `uv add a2a-sdk==1.1.3` cannot resolve it).

The public `Publish Python Package` run for the release built the wheel and sdist successfully, but its `pypi-publish` job failed during distribution validation:

```shell
Checking dist/a2a_sdk-1.1.3-py3-none-any.whl: ERROR InvalidDistribution: Invalid distribution metadata: '2.5' is not a valid metadata version
```

Relevant links:

- Release: https://github.com/a2aproject/a2a-python/releases/tag/v1.1.3
- Failed workflow: https://github.com/a2aproject/a2a-python/actions/runs/32121352210
- Failed publish job: https://github.com/a2aproject/a2a-python/actions/runs/32121352210/job/95662307403
- Existing dependency update PR #1187 upgrades `pypa/gh-action-pypi-publish` from 1.14.0 to 1.14.2. The 1.14.2 release notes specifically mention support for uploading distributions with Core Metadata 2.5.

It looks like the release artifacts use Core Metadata 2.5 while the pinned publishing action's validation tooling does not yet accept it. Could you please confirm that v1.1.3 is intended to be published to PyPI and, if so, update/rerun the publishing path?

I am happy to help verify installation once the release is available. Thanks again!

## Relevant log output

```shell
Checking dist/a2a_sdk-1.1.3-py3-none-any.whl: ERROR InvalidDistribution: Invalid distribution metadata: '2.5' is not a valid metadata version
```

## Code of Conduct

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