fix(reddit,bilibili): switch to rdt-cli and add bili-cli support (#235)

Reddit: Exa crawling had chronic CRAWL_LIVECRAWL_TIMEOUT issues.
rdt-cli (304 stars, public-clis) works without login — search, read
full posts, and comments all verified. Massive improvement.

Bilibili: add bili-cli (590 stars) as optional enhanced backend for
hot/rank/search/feed. yt-dlp remains for video metadata + subtitles.

Also fix UA string (was "agent-reach/1.0", now proper browser UA).

75 tests passing.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

agent_reach/channels/reddit.py

@@ -1,30 +1,15 @@
 # -*- coding: utf-8 -*-
-"""Reddit — search and read via Exa (no direct Reddit API needed)."""
+"""Reddit — search and read via rdt-cli (public-clis/rdt-cli)."""
 
 import shutil
 import subprocess
 from .base import Channel
 
 
-def _exa_available() -> bool:
-    """Return True if mcporter is installed and Exa MCP is configured."""
-    mcporter = shutil.which("mcporter")
-    if not mcporter:
-        return False
-    try:
-        r = subprocess.run(
-            [mcporter, "config", "list"], capture_output=True,
-            encoding="utf-8", errors="replace", timeout=5
-        )
-        return "exa" in r.stdout.lower()
-    except Exception:
-        return False
-
-
 class RedditChannel(Channel):
     name = "reddit"
-    description = "Reddit 帖子和评论（通过 Exa 搜索和阅读）"
-    backends = ["Exa via mcporter"]
+    description = "Reddit 帖子和评论"
+    backends = ["rdt-cli"]
     tier = 0
 
     def can_handle(self, url: str) -> bool:
@@ -33,10 +18,14 @@ class RedditChannel(Channel):
         return "reddit.com" in d or "redd.it" in d
 
     def check(self, config=None):
-        if _exa_available():
-            return "ok", "通过 Exa 搜索和阅读 Reddit 内容（免费，无需代理）"
+        rdt = shutil.which("rdt")
+        if rdt:
+            return "ok", (
+                "rdt-cli 可用（搜索帖子、阅读全文、查看评论，无需登录）"
+            )
         return "off", (
-            "需要 mcporter + Exa MCP。安装：\n"
-            "  npm install -g mcporter\n"
-            "  mcporter config add exa https://mcp.exa.ai/mcp"
+            "需要安装 rdt-cli：\n"
+            "  pipx install rdt-cli\n"
+            "或：\n"
+            "  uv tool install rdt-cli"
         )