Add demo trio personas and polish empty-state panel UX.

Build credentials during Phase 1 and streamline human participant setup.

feat(conversation): pluggable structures + decision methods (Robert's Rules, ranked-choice, majority)

feat: human participant turns + credential intake redesign

feat(participants): add "Select N Automatically" option

feat(limits): expose repetition / failsafe limits in settings menu

Build CCAI Vibe Demo on top of LLMChats3 baseline