Add `--wait` flag to `commit create`

[AlephNotation]

Feature request

vers run, vers branch, and vers resume all support --wait to block until the operation completes. vers commit create does not, even though the commit may not be immediately usable (e.g., for run-commit or branch).

Suggestion

vers commit create --wait              # block until commit is ready
vers commit create --wait --format json  # return JSON when done

Impact

Without --wait, agents must poll or add arbitrary sleep delays before using a newly created commit. This is particularly relevant for workflows like commit → branch-from-commit.