feat: 新增 YouTube/Bilibili/XHS 搜索 CLI 命令 + 修复 B站搜索

- cli.py: 新增 search-youtube / search-bilibili / search-xhs 子命令
- core.py: 新增 search_youtube / search_bilibili / search_xhs 方法
- bilibili.py: 搜索策略改为 yt-dlp → Exa fallback（服务器 IP 被 B站 412）
  - 本地机器走 yt-dlp bilisearch（有 title/uploader）
  - 服务器自动 fallback 到 Exa site:bilibili.com
  - 修复 mcporter 输出解析（Title:/URL: 格式）

测试结果: 15/15 全通（8 read + 7 search）

agent_reach/cli.py

@@ -66,6 +66,21 @@ def main():
     p_st.add_argument("query", nargs="+", help="Search query")
     p_st.add_argument("-n", "--num", type=int, default=10, help="Number of results")
 
+    # ── search-youtube ──
+    p_sy = sub.add_parser("search-youtube", help="Search YouTube")
+    p_sy.add_argument("query", nargs="+", help="Search query")
+    p_sy.add_argument("-n", "--num", type=int, default=5, help="Number of results")
+
+    # ── search-bilibili ──
+    p_sb = sub.add_parser("search-bilibili", help="Search Bilibili")
+    p_sb.add_argument("query", nargs="+", help="Search query")
+    p_sb.add_argument("-n", "--num", type=int, default=5, help="Number of results")
+
+    # ── search-xhs ──
+    p_sx = sub.add_parser("search-xhs", help="Search XiaoHongShu")
+    p_sx.add_argument("query", nargs="+", help="Search query")
+    p_sx.add_argument("-n", "--num", type=int, default=10, help="Number of results")
+
     # ── setup ──
     sub.add_parser("setup", help="Interactive configuration wizard")
 
@@ -575,6 +590,12 @@ async def _cmd_search(args):
             results = await eyes.search_github(query, language=getattr(args, "lang", None), limit=num)
         elif args.command == "search-twitter":
             results = await eyes.search_twitter(query, limit=num)
+        elif args.command == "search-youtube":
+            results = await eyes.search_youtube(query, limit=num)
+        elif args.command == "search-bilibili":
+            results = await eyes.search_bilibili(query, limit=num)
+        elif args.command == "search-xhs":
+            results = await eyes.search_xhs(query, limit=num)
         else:
             print(f"Unknown command: {args.command}", file=sys.stderr)
             sys.exit(1)