Less of a mess if you use a YAML block literal (basically a heredoc):

    jobs:
      format:
        runs-on: ubuntu-latest
        if: |
          ! contains(github.event.head_commit.message, ‘wip’)

Other systems that output YAML (e.g. Kubernetes) always emit block literals for embedded user-supplied strings, reserving inline string literals for the cases where the string isn’t expected to need quoting — e.g. string-serialized enum option-values; symbol/atom/keyword-typed values; and sometimes URLs.