Extend the stage registry with presentation metadata (icon/label/glob) so adding
a stage stays data-only. Add CeFlow renderer for text/single_select/multi_select/
confirm questions over the U5 polling session routes, with a visibly-marked chat
fallback (AE1) that still completes the stage. Wire the artifact-hub launcher to
list and start registered stages. Add the skill-interaction audit test producing
a measured rich-vs-chat coverage ratio (declared classification: 8/8=100% across
brainstorm/ideate/plan), failing on unclassified interactions.