Catalog v6.2.1

groundskeeper: iterationCreate now sends the required groupPath. The
omission passed GraphQL validation (groupPath and projectPath are
individually nullable; exactly one is enforced only at resolution) and
stopped v6.2.0's first real apply fail-closed after milestone_window's
batch had landed. The offline fake now enforces both mutations'
required arguments, so this class fails the test suite instead of the
estate.