The YAML compiler was using SubWorkflowPlaceholderStep that returned
next() immediately. Replaced with real SubWorkflowStep from wfe-core
that starts child workflows and waits for completion events.
Added regression test verifying the compiled factory produces a step
that calls host_context.start_workflow() and returns wait_for_event.
Compiler dispatches type: workflow to SubWorkflowStep. Validation
detects circular workflow references via DFS with coloring. Cross-
workflow reference checking for multi-workflow files. Duplicate
workflow ID detection. 28 edge case tests for validation paths.
Standalone workspace crates for BuildKit image building and containerd
container execution. Config types, YAML schema integration, compiler
dispatch, validation rules, and mock-based unit tests.
Current implementation shells out to buildctl/nerdctl — will be
replaced with proper gRPC clients (buildkit-client, containerd protos)
in a follow-up. Config types, YAML integration, and test infrastructure
are stable and reusable.
wfe-buildkit: 60 tests, 97.9% library coverage
wfe-containerd: 61 tests, 97.8% library coverage
447 total workspace tests.
