refactor: strip to installer + doctor + docs, remove read/search wrapper layer

BREAKING CHANGE: Remove all `agent-reach read` and `agent-reach search-*` commands.

Agent Reach is now an installer, configuration tool, and doctor —
not a wrapper layer. After installation, agents call upstream tools
directly (bird CLI, yt-dlp, mcporter, gh CLI, Jina Reader, etc.).

What's kept:
- agent-reach install: one-shot installer
- agent-reach doctor: channel status overview
- agent-reach configure: cookies, proxy, credentials
- agent-reach setup: interactive wizard
- SKILL.md: complete guide for agents to use upstream tools directly

What's removed:
- agent-reach read URL (and all channel read() methods)
- agent-reach search-* commands (and all channel search() methods)
- ReadResult / SearchResult data classes
- URL routing system (get_channel_for_url)
- All parsing/conversion logic (VTT, Reddit JSON, bird text parser, etc.)
- MCP server read/search tools (kept only get_status)

Net change: -1790 lines. Less code = fewer bugs.

agent_reach/channels/youtube.py

@@ -1,125 +1,22 @@
 # -*- coding: utf-8 -*-
-"""YouTube — via yt-dlp (video info, subtitles, and search).
+"""YouTube — check if yt-dlp is available."""
 
-Backend: yt-dlp (https://github.com/yt-dlp/yt-dlp)
-Supports: read (info + subtitles), search (ytsearch)
-"""
-
-import json
 import shutil
-import subprocess
-import tempfile
-from pathlib import Path
-from urllib.parse import urlparse
-from .base import Channel, ReadResult, SearchResult
-from typing import List
+from .base import Channel
 
 
 class YouTubeChannel(Channel):
     name = "youtube"
-    description = "YouTube 视频字幕"
+    description = "YouTube 视频和字幕"
     backends = ["yt-dlp"]
-    requires_tools = ["yt-dlp"]
     tier = 0
 
     def can_handle(self, url: str) -> bool:
+        from urllib.parse import urlparse
         d = urlparse(url).netloc.lower()
         return "youtube.com" in d or "youtu.be" in d
 
-    async def read(self, url: str, config=None) -> ReadResult:
-        if not shutil.which("yt-dlp"):
-            raise RuntimeError("yt-dlp not installed. Install: pip install yt-dlp")
-
-        with tempfile.TemporaryDirectory() as tmpdir:
-            info = self._get_info(url)
-            title = info.get("title", url)
-            author = info.get("uploader", "")
-
-            transcript = self._get_subtitles(url, tmpdir)
-            if not transcript:
-                transcript = f"[Video: {title}]\n[No subtitles available.]"
-
-            return ReadResult(
-                title=title, content=transcript, url=url,
-                author=author, platform="youtube",
-                extra={
-                    "duration": info.get("duration_string"),
-                    "view_count": info.get("view_count"),
-                    "upload_date": info.get("upload_date"),
-                },
-            )
-
-    async def search(self, query: str, config=None, **kwargs) -> List[SearchResult]:
-        """Search YouTube via yt-dlp's ytsearch."""
-        if not shutil.which("yt-dlp"):
-            raise RuntimeError("yt-dlp not installed. Install: pip install yt-dlp")
-
-        limit = kwargs.get("limit", 10)
-
-        try:
-            r = subprocess.run(
-                ["yt-dlp", "--dump-json", "--flat-playlist",
-                 f"ytsearch{limit}:{query}"],
-                capture_output=True, text=True, timeout=30,
-            )
-            results = []
-            for line in r.stdout.strip().split("\n"):
-                if not line.strip():
-                    continue
-                try:
-                    d = json.loads(line)
-                    vid = d.get("id", "")
-                    results.append(SearchResult(
-                        title=d.get("title", ""),
-                        url=f"https://youtube.com/watch?v={vid}" if vid else "",
-                        snippet=(
-                            f"👤 {d.get('channel', '?')} · "
-                            f"⏱ {d.get('duration_string', '?')} · "
-                            f"👁 {d.get('view_count', '?')}"
-                        ),
-                        extra={
-                            "channel": d.get("channel"),
-                            "duration": d.get("duration_string"),
-                            "view_count": d.get("view_count"),
-                        },
-                    ))
-                except json.JSONDecodeError:
-                    continue
-            return results
-        except subprocess.TimeoutExpired:
-            return []
-
-    def _get_info(self, url: str) -> dict:
-        try:
-            r = subprocess.run(
-                ["yt-dlp", "--dump-json", "--no-download", url],
-                capture_output=True, text=True, timeout=30,
-            )
-            if r.returncode == 0:
-                return json.loads(r.stdout)
-        except (subprocess.TimeoutExpired, json.JSONDecodeError):
-            pass
-        return {}
-
-    def _get_subtitles(self, url: str, tmpdir: str) -> str:
-        try:
-            subprocess.run(
-                ["yt-dlp", "--write-auto-sub", "--write-sub",
-                 "--sub-lang", "en,zh-Hans,zh",
-                 "--skip-download", "--sub-format", "vtt",
-                 "-o", f"{tmpdir}/%(id)s.%(ext)s", url],
-                capture_output=True, text=True, timeout=30,
-            )
-            for f in Path(tmpdir).glob("*.vtt"):
-                text = f.read_text(errors="replace")
-                lines = []
-                for line in text.split("\n"):
-                    line = line.strip()
-                    if not line or line.startswith("WEBVTT") or "-->" in line or line.isdigit():
-                        continue
-                    if line not in lines[-1:]:
-                        lines.append(line)
-                return "\n".join(lines)
-        except subprocess.TimeoutExpired:
-            pass
-        return ""
+    def check(self, config=None):
+        if shutil.which("yt-dlp"):
+            return "ok", "可提取视频信息和字幕"
+        return "off", "yt-dlp 未安装。安装：pip install yt-dlp"