chore: 移除所有 Citations 相关逻辑，为后续重构做准备

- Backend: 删除 lead_agent / general_purpose 中的 citations_format 与引用相关 reminder；artifacts 下载不再对 markdown 做 citation 清洗，统一走 FileResponse，保留 Response 用于二进制 inline
- Frontend: 删除 core/citations 模块、inline-citation、safe-citation-content；新增 MarkdownContent 仅做 Markdown 渲染；消息/artifact 预览与复制均使用原始 content
- i18n: 移除 citations 命名空间（loadingCitations、loadingCitationsWithCount）
- 技能与 demo: 措辞改为 references，demo 数据去掉 <citations> 块
- 文档: 更新 CLAUDE/AGENTS/README 描述，新增按文件 diff 的代码变更总结

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/public/demo/threads/fe3f7974-1bcb-4a01-a950-79673baafefd/user-data/outputs/research_deerflow_20260201.md

@@ -1,12 +1,3 @@
-<citations>
-{"id": "cite-1", "title": "DeerFlow GitHub Repository", "url": "https://github.com/bytedance/deer-flow", "snippet": "Community-driven Deep Research framework combining language models with tools like web search, crawling, and Python execution"}
-{"id": "cite-2", "title": "Create Your Own Deep Research Agent with DeerFlow", "url": "https://thesequence.substack.com/p/the-sequence-engineering-661-create", "snippet": "Open-source multi-agent research automation framework developed by ByteDance"}
-{"id": "cite-3", "title": "DeerFlow: A Game-Changer for Automated Research and Content Creation", "url": "https://medium.com/@mingyang.heaven/deerflow-a-game-changer-for-automated-research-and-content-creation-83612f683e7a", "snippet": "Open-source multi-agent framework revolutionizing research and content creation"}
-{"id": "cite-4", "title": "ByteDance DeerFlow - (Deep Research Agents with a LOCAL LLM!)", "url": "https://www.youtube.com/watch?v=Ui0ovCVDYGs", "snippet": "Video demonstration of DeerFlow capabilities and local LLM integration"}
-{"id": "cite-5", "title": "DeerFlow Official Website", "url": "https://deerflow.tech/", "snippet": "Official platform showcasing DeerFlow features, case studies, and architecture"}
-{"id": "cite-6", "title": "Navigating the Landscape of Deep Research Frameworks", "url": "https://www.oreateai.com/blog/navigating-the-landscape-of-deep-research-frameworks-a-comprehensive-comparison/0dc13e48eb8c756650112842c8d1a184", "snippet": "Comparative analysis of deep research frameworks including DeerFlow"}
-{"id": "cite-7", "title": "DeerFlow: Multi-Agent AI For Research Automation 2025", "url": "https://firexcore.com/blog/what-is-deerflow/", "snippet": "Overview of DeerFlow features and capabilities for research automation"}
-</citations>
 # DeerFlow Deep Research Report
 
 - **Research Date:** 2026-02-01