Surface all seven WORKFLOW_STEP_TEMPLATES add-ons in the editor's Built-in steps
palette with two insert variants: as a single node (existing stepTemplateToNode)
and as an optional-group-wrapped subgraph (optionalGroupFragmentIr + the existing
insertFragment path, which already expands optional-group children). Also update
the cross-package built-in failure-edge parity assertion for U6's
workflow-step -> browser-verification optional-group migration.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>