Fix git push authentication failure in release workflow

[Copilot]

The workflow failed when pushing tags with fatal: could not read Username for 'https://github.com': No such device or address. The git push origin command couldn't authenticate over HTTPS because no credentials were configured.

Changes

• Configure git credential helper to cache authentication in memory (300s timeout)
• Provide GitHub token via git credential approve using here-document syntax
• Token stays out of command-line arguments and git URLs

git config --global credential.helper 'cache --timeout=300'
git credential approve <<EOF
protocol=https
host=github.com
username=x-access-token
password=${GH_TOKEN}
EOF
git push origin "${TAG_NAME}"

The credential helper approach is more secure than embedding tokens in URLs and follows GitHub Actions best practices.

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