Improve mobile header and participants dropdown UX.

Build credentials during Phase 1 and streamline human participant setup.

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

feat(resilience): multi-tier participant failure recovery + Response-priority toggle

refactor(ui): shorten Settings menu — accordions + Model Selection merge

feat(ui): header cleanup + Table View shortcut + post-chat downloads strip

feat: human participant turns + credential intake redesign

feat(ui): consolidate downloads, move theme into settings, restructure & darken settings menu, fix max-participants prop wiring

rename: 'CCAI Vibe Demo' -> 'Collaborative Conversational AI (CCAI) Demo'

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

Build CCAI Vibe Demo on top of LLMChats3 baseline