feat: 新增 Instagram、LinkedIn、Boss直聘 三个渠道

新增渠道：
- Instagram: 基于 instaloader (⭐9.8K)，读取帖子/Profile，Cookie 登录
- LinkedIn: 基于 linkedin-scraper-mcp (⭐900+) MCP 服务，Jina Reader fallback
- Boss直聘: 基于 mcp-bosszp MCP 服务，Jina Reader fallback

代码改动：
- 新建 channels/instagram.py, linkedin.py, bosszhipin.py
- 注册到 channels/__init__.py
- cli.py 添加 search-instagram/linkedin/bosszhipin 子命令
- cli.py 安装逻辑添加 instaloader 自动安装
- core.py 添加 search_instagram/linkedin/bosszhipin 方法
- README.md + docs/README_en.md 更新平台表格和选型表格
- docs/install.md 添加三个新渠道的配置说明和 Quick Reference

agent_reach/cli.py

@@ -89,6 +89,21 @@ def main():
     p_sx.add_argument("query", nargs="+", help="Search query")
     p_sx.add_argument("-n", "--num", type=int, default=10, help="Number of results")
 
+    # ── search-instagram ──
+    p_si = sub.add_parser("search-instagram", help="Search Instagram")
+    p_si.add_argument("query", nargs="+", help="Search query")
+    p_si.add_argument("-n", "--num", type=int, default=10, help="Number of results")
+
+    # ── search-linkedin ──
+    p_sl = sub.add_parser("search-linkedin", help="Search LinkedIn")
+    p_sl.add_argument("query", nargs="+", help="Search query")
+    p_sl.add_argument("-n", "--num", type=int, default=10, help="Number of results")
+
+    # ── search-bosszhipin ──
+    p_sbz = sub.add_parser("search-bosszhipin", help="Search Boss直聘")
+    p_sbz.add_argument("query", nargs="+", help="Search query")
+    p_sbz.add_argument("-n", "--num", type=int, default=10, help="Number of results")
+
     # ── setup ──
     sub.add_parser("setup", help="Interactive configuration wizard")
 
@@ -369,6 +384,23 @@ def _install_system_deps():
         else:
             print("  ⬜ bird CLI requires Node.js (optional — Twitter reading still works via Jina)")
 
+    # ── instaloader (for Instagram) ──
+    if shutil.which("instaloader"):
+        print("  ✅ instaloader already installed")
+    else:
+        print("  📥 Installing instaloader...")
+        try:
+            subprocess.run(
+                [sys.executable, "-m", "pip", "install", "instaloader"],
+                capture_output=True, text=True, timeout=120,
+            )
+            if shutil.which("instaloader"):
+                print("  ✅ instaloader installed (Instagram reading)")
+            else:
+                print("  ⬜ instaloader install failed (optional — try: pip install instaloader)")
+        except Exception:
+            print("  ⬜ instaloader install failed (optional — try: pip install instaloader)")
+
 
 def _install_mcporter():
     """Install mcporter and configure Exa + XiaoHongShu MCP servers."""
@@ -761,6 +793,12 @@ async def _cmd_search(args):
             results = await eyes.search_bilibili(query, limit=num)
         elif args.command == "search-xhs":
             results = await eyes.search_xhs(query, limit=num)
+        elif args.command == "search-instagram":
+            results = await eyes.search_instagram(query, limit=num)
+        elif args.command == "search-linkedin":
+            results = await eyes.search_linkedin(query, limit=num)
+        elif args.command == "search-bosszhipin":
+            results = await eyes.search_bosszhipin(query, limit=num)
         else:
             print(f"Unknown command: {args.command}", file=sys.stderr)
             sys.exit(1)