Upgrading dependencies causes a regression in the R2 upload

https://github.com/astral-sh/python-build-standalone/pull/1044 was required to resolve persistent release failures like:

```
Running `target/release/pythonbuild upload-mirror-distributions --dist dist --datetime 20260324T0736 --tag 20260324 --bucket *** --prefix github/python-build-standalone/releases/download/20260324/`
found all 852 release artifacts
uploading cpython-3.10.20-aarch64-apple-darwin-debug-20260324T0736.tar.zst -> s3://***/github/python-build-standalone/releases/download/20260324/cpython-3.10.20+20260324-aarch64-apple-darwin-debug-full.tar.zst
uploading cpython-3.10.20-aarch64-apple-darwin-install_only-20260324T0736.tar.gz -> s3://***/github/python-build-standalone/releases/download/20260324/cpython-3.10.20+20260324-aarch64-apple-darwin-install_only.tar.gz
uploading cpython-3.10.20-aarch64-apple-darwin-install_only_stripped-20260324T0736.tar.gz -> s3://***/github/python-build-standalone/releases/download/20260324/cpython-3.10.20+20260324-aarch64-apple-darwin-install_only_stripped.tar.gz
uploading cpython-3.10.20-aarch64-apple-darwin-pgo+lto-20260324T0736.tar.zst -> s3://***/github/python-build-standalone/releases/download/20260324/cpython-3.10.20+20260324-aarch64-apple-darwin-pgo+lto-full.tar.zst
uploading cpython-3.10.20-aarch64-unknown-linux-gnu-debug-20260324T0736.tar.zst -> s3://***/github/python-build-standalone/releases/download/20260324/cpython-3.10.20+20260324-aarch64-unknown-linux-gnu-debug-full.tar.zst
uploading cpython-3.10.20-aarch64-unknown-linux-gnu-install_only-20260324T0736.tar.gz -> s3://***/github/python-build-standalone/releases/download/20260324/cpython-3.10.20+20260324-aarch64-unknown-linux-gnu-install_only.tar.gz
uploading cpython-3.10.20-aarch64-unknown-linux-gnu-install_only_stripped-20260324T0736.tar.gz -> s3://***/github/python-build-standalone/releases/download/20260324/cpython-3.10.20+20260324-aarch64-unknown-linux-gnu-install_only_stripped.tar.gz
uploading cpython-3.10.20-aarch64-unknown-linux-gnu-pgo+lto-20260324T0736.tar.zst -> s3://***/github/python-build-standalone/releases/download/20260324/cpython-3.10.20+20260324-aarch64-unknown-linux-gnu-pgo+lto-full.tar.zst
Error: dispatch failure

Caused by:
0: io error
1: client error (SendRequest)
2: connection error
3: Connection reset by peer (os error 104)
error: Recipe `release-upload-mirror` failed with exit code 1
```

We have yet to determine the root cause, but should investigate. It seems like no uploads can succeed.

Start by reviewing PR 1044 and reproducing the release-upload-mirror command shown in the issue. Investigate why the R2/S3-compatible upload receives a connection reset after dependency upgrades; done means identifying the regression and restoring successful uploads for the release artifacts.

Written by the indexing model from the issue text.