Built-in (builtin:*) workflows are read-only at the store layer; reflect
that in the editor so users aren't misled into editing changes that can't
save. For a built-in: the node palette is disabled, the inspector fields are
wrapped in a disabled fieldset, Save/Delete are replaced by a "Read-only
built-in" label, and a "Duplicate to edit" action clones it into an editable
user workflow. handleSave/handleDeleteWorkflow also early-return for built-ins
as defense-in-depth.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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