feat(skill): refactor skill system with router + references structure (#192)

Refactors SKILL.md into a router + reference documentation system:
- Main SKILL.md now contains routing table and quick commands
- Detailed docs split into references/ (search, social, career, dev, web, video)
- CLI skill install copies entire directory including references/
- Resolves conflicts with recent merges (#210, #213)
- Fixes xreach→bird in quick commands

Original PR by @Citrus086, merged with conflict resolution.

Co-Authored-By: Citrus086 <Citrus086@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

agent_reach/skill/references/social.md

@@ -0,0 +1,149 @@
+# 社交媒体 & 社区
+
+小红书、抖音、Twitter/X、微博、B站、V2EX、Reddit。
+
+## 小红书 / XiaoHongShu
+
+```bash
+# 搜索笔记
+mcporter call 'xiaohongshu.search_feeds(keyword: "query")'
+
+# 获取笔记详情
+mcporter call 'xiaohongshu.get_feed_detail(feed_id: "xxx", xsec_token: "yyy")'
+
+# 获取笔记详情 + 评论
+mcporter call 'xiaohongshu.get_feed_detail(feed_id: "xxx", xsec_token: "yyy", load_all_comments: true)'
+
+# 发布内容
+mcporter call 'xiaohongshu.publish_content(title: "标题", content: "正文", images: ["/path/img.jpg"], tags: ["tag"])'
+```
+
+> **需要登录**: 使用 Cookie-Editor 浏览器插件导出 cookies。运行 `agent-reach doctor` 检查状态。
+
+## 抖音 / Douyin
+
+```bash
+# 解析视频信息
+mcporter call 'douyin.parse_douyin_video_info(share_link: "https://v.douyin.com/xxx/")'
+
+# 获取无水印下载链接
+mcporter call 'douyin.get_douyin_download_link(share_link: "https://v.douyin.com/xxx/")'
+
+# 提取视频文案
+mcporter call 'douyin.extract_douyin_text(share_link: "https://v.douyin.com/xxx/")'
+```
+
+> **无需登录**
+
+## Twitter/X (xreach CLI)
+
+```bash
+# 搜索推文
+xreach search "query" -n 10 --json
+
+# 读取单条推文 (支持 /status/ 和 /article/ URL)
+xreach tweet URL_OR_ID --json
+
+# 用户时间线
+xreach tweets @username -n 20 --json
+
+# 读取完整 thread
+xreach thread URL_OR_ID --json
+```
+
+> **需要配置**: `agent-reach configure twitter-auth ...` 或通过环境变量配置。
+> 如果 fetch 失败，确保安装了 undici: `npm install -g undici`
+
+## 微博 / Weibo
+
+```bash
+# 使用 Jina Reader 读取
+curl -s "https://r.jina.ai/https://weibo.com/USER_ID/POST_ID"
+```
+
+> 微博主要通过网页抓取，推荐使用通用网页读取方式。
+
+## B站 / Bilibili
+
+```bash
+# 获取视频元数据
+yt-dlp --dump-json "https://www.bilibili.com/video/BVxxx"
+
+# 下载字幕
+yt-dlp --write-sub --write-auto-sub --sub-lang "zh-Hans,zh,en" --convert-subs vtt --skip-download -o "/tmp/%(id)s" "URL"
+```
+
+> **注意**: 服务器 IP 可能遇到 412 错误。使用 `--cookies-from-browser chrome` 或配置代理。
+
+## V2EX (公开 API)
+
+无需认证，直接调用公开 API。
+
+### 热门主题
+
+```bash
+curl -s "https://www.v2ex.com/api/topics/hot.json" -H "User-Agent: agent-reach/1.0"
+```
+
+### 节点主题
+
+```bash
+# node_name 如: python, tech, jobs, qna, programmers
+curl -s "https://www.v2ex.com/api/topics/show.json?node_name=python&page=1" -H "User-Agent: agent-reach/1.0"
+```
+
+### 主题详情
+
+```bash
+# topic_id 从 URL 获取，如 https://www.v2ex.com/t/1234567
+curl -s "https://www.v2ex.com/api/topics/show.json?id=TOPIC_ID" -H "User-Agent: agent-reach/1.0"
+```
+
+### 主题回复
+
+```bash
+curl -s "https://www.v2ex.com/api/replies/show.json?topic_id=TOPIC_ID&page=1" -H "User-Agent: agent-reach/1.0"
+```
+
+### 用户信息
+
+```bash
+curl -s "https://www.v2ex.com/api/members/show.json?username=USERNAME" -H "User-Agent: agent-reach/1.0"
+```
+
+### Python 调用示例
+
+```python
+from agent_reach.channels.v2ex import V2EXChannel
+
+ch = V2EXChannel()
+
+# 获取热门帖子
+topics = ch.get_hot_topics(limit=10)
+for t in topics:
+    print(f"[{t['node_title']}] {t['title']} ({t['replies']} 回复)")
+
+# 获取节点帖子
+node_topics = ch.get_node_topics("python", limit=5)
+
+# 获取帖子详情 + 回复
+topic = ch.get_topic(1234567)
+print(topic["title"], "—", topic["author"])
+
+# 获取用户信息
+user = ch.get_user("Livid")
+```
+
+> **节点列表**: https://www.v2ex.com/planes
+
+## Reddit (公开 API)
+
+```bash
+# 获取 subreddit 热门帖子
+curl -s "https://www.reddit.com/r/SUBREDDIT/hot.json?limit=10" -H "User-Agent: agent-reach/1.0"
+
+# 搜索
+curl -s "https://www.reddit.com/search.json?q=QUERY&limit=10" -H "User-Agent: agent-reach/1.0"
+```
+
+> **注意**: 服务器 IP 可能遇到 403 错误。搜索建议使用 Exa 代替，或配置代理。