Frontend:
- Add Discord-style 3-column layout (server icons / channel sidebar / chat)
- AI Studio design system: new CSS token palette (--room-* vars)
- Replace all hardcoded Discord colors with CSS variable tokens
- Add RoomSettingsPanel (name, visibility, AI model management)
- Settings + Member list panels mutually exclusive (don't overlap)
- AI models shown at top of member list with green accent
- Fix TS errors: TipTap SuggestionOptions, unused imports, StarterKit options
- Remove MentionInput, MentionPopover, old room components (废弃代码清理)
Backend:
- RoomAiResponse returns model_name from agents.model JOIN
- room_ai_list and room_ai_upsert fetch model name for each config
- AiConfigData ws-protocol interface updated with model_name
Note: RoomSettingsPanel UI still uses shadcn defaults (未完全迁移到AI Studio)
