Captured step values of mesh-build-image (fetch, a candidate's build, a trunk's build), copied from
novox/mesh-catalog modules/mesh-build-image/cmd/mesh-build-image/testdata/captured/. Both copies must change together: the
module's capture test writes them, and the builder's TestCapturedImageStepsDecodeWithTheBuildersOwnTypes (internal/build,
fixtures_test.go) decodes these with the types the builder reads results with and fails on a missing field.