feat: auto-install WeChat article tools during install (#80)

* feat: auto-install WeChat article tools during agent-reach install

WeChat (微信公众号) deps are now auto-installed during 'agent-reach install':
- Python packages: camoufox[geoip], markdownify, beautifulsoup4, httpx, miku_ai
- Tool repo: wechat-article-for-ai cloned to ~/.agent-reach/tools/

No login or configuration needed — works out of the box like YouTube/RSS.
Updated README tables to reflect zero-config status.
Also covers safe mode and dry-run.

* feat: auto-install WeChat + add channel-setup reference to SKILL.md

1. WeChat auto-install during 'agent-reach install':
   - pip install camoufox[geoip], markdownify, bs4, httpx, miku_ai
   - clone wechat-article-for-ai to ~/.agent-reach/tools/
   - covers safe mode and dry-run
   - README tables: WeChat → zero-config

2. SKILL.md improvements:
   - Added 'configure' triggers to description
   - Added references/channel-setup.md with install steps for all
     login-required platforms (Twitter, XHS, Douyin, LinkedIn, Boss)
   - Principle: user only provides cookies, agent does everything else

* simplify: point to install.md URL instead of bundled reference

No need to maintain a separate channel-setup.md. Just tell agents
to fetch install.md when they need setup instructions.

---------

Co-authored-by: Panniantong <panniantong@users.noreply.github.com>

agent_reach/skill/SKILL.md

@@ -7,12 +7,14 @@ description: >
   Use when: (1) user asks to search or read any of these platforms,
   (2) user shares a URL from any supported platform,
   (3) user asks to search the web, find information online, or research a topic,
-  (4) user asks to post, comment, or interact on supported platforms.
+  (4) user asks to post, comment, or interact on supported platforms,
+  (5) user asks to configure or set up a platform channel.
   Triggers: "搜推特", "搜小红书", "看视频", "搜一下", "上网搜", "帮我查", "全网搜索",
   "search twitter", "read tweet", "youtube transcript", "search reddit",
   "read this link", "看这个链接", "B站", "bilibili", "抖音视频",
   "微信文章", "公众号", "LinkedIn", "GitHub issue", "RSS",
-  "search online", "web search", "find information", "research".
+  "search online", "web search", "find information", "research",
+  "帮我配", "configure twitter", "configure proxy", "帮我安装".
 ---
 
 # Agent Reach — Usage Guide
@@ -157,4 +159,10 @@ for e in feedparser.parse('FEED_URL').entries[:5]:
 
 - **Channel not working?** Run `agent-reach doctor` — shows status and fix instructions.
 - **Twitter fetch failed?** Ensure `undici` is installed: `npm install -g undici`. Configure proxy: `agent-reach configure proxy URL`.
-- **Need to configure a channel?** Run `agent-reach doctor`, follow its instructions, or tell user to run the install guide.
+
+## Setting Up a Channel ("帮我配 XXX")
+
+If a channel needs setup (cookies, Docker, etc.), fetch the install guide:
+https://raw.githubusercontent.com/Panniantong/agent-reach/main/docs/install.md
+
+User only provides cookies. Everything else is your job.