[eschaar]

Summary

• Serialize manual and dispatched formula updates in one concurrency group without cancelling a running update.
• Check out current main when an update starts, avoiding stale event snapshots after queueing.
• Run Homebrew checks when the updater workflow changes; document the update lifecycle.

Why

The 4.1.1 update conflicted with a concurrent 4.1.0 formula update at rebase/push. Both jobs started from the same older main commit.

Validation

• YAML contract check fails on the original workflow and passes with serialization and current-main checkout.
• Confirmed dispatch inputs, permissions and formula generation steps remain unchanged.
• Actual 4.1.1 update retried separately with verified PyPI URL and checksum; Homebrew install/test/audit results will be checked before completion.

[eschaar]

Verified recovery and current PR head:

• Version 4.1.1 formula update succeeded: https://github.com/eschaar/homebrew-vstack/actions/runs/40412313813
• Main formula URL/checksum match PyPI 4.1.1 metadata.
• Actual macOS installation, formula test and audit all passed on main: https://github.com/eschaar/homebrew-vstack/actions/runs/40412650924
• This PR was updated with the 4.1.1 formula; its installation, test and audit also passed: https://github.com/eschaar/homebrew-vstack/actions/runs/40412715982
• Static before/after YAML contract confirmed the concurrency/latest-main fix and unchanged dispatch inputs, permissions and generation steps.