Add the minor changeset for the optional-group feature (U1-U6) and document in
the plan why the full legacy optional-steps retirement (U7) is deferred: the
workflow-step seam is shared engine infrastructure across ~9 files and the
dashboard still carries the prior declaration authoring surface (~10 files), so
removing the core type without that cleanup breaks the build. The new model is
the live path; the legacy declaration surface is inert pending a focused follow-up.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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