Summary

This PR hardens the release README update workflow so it only commits the intended README.md release-section change after a GitHub Release is published.

The previous workflow could fail when the runner detected unrelated working-tree changes, such as workflow files or Directory.Packages.props being marked modified by checkout or normalization behavior. When peter-evans/create-pull-request attempted to create or switch to the docs/update-latest-release branch, Git refused because those unrelated local changes would have been overwritten.

Changes

• Updated the checkout step to use a clean, full checkout of main.
• Added protection to restore any non-README.md working-tree changes before creating the PR.
• Restricted peter-evans/create-pull-request to stage only README.md.
• Preserved the existing release-marker replacement logic.
• Kept the generated PR branch, title, body, and delete-branch behavior unchanged.

Why

This keeps the release automation narrowly scoped to the README latest-release block and prevents unrelated line-ending, dependency, or workflow-file normalization changes from breaking the automated PR creation step.

Validation

• This is a workflow-only change.
• The next published release should create a README update PR containing only README.md.
• Existing release PR preparation and package publication behavior are unchanged.