* test(#4183): reproduce root phase Fallow base failure
* fix(#4183): resolve root phase Fallow base
Fall back to the phase root commit when its parent is unresolvable.
* chore(#4183): add release note
* chore(#4183): bind changeset to fork PR
* docs(#4183): describe root fallback precisely
* chore(#4183): bind changeset to upstream PR
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Co-authored-by: CI Rebase Check <ci@gsd-redux>
Co-authored-by: Tom Boucher <trekkie@nomorestars.com>
