rename: Agent Eyes → Agent Reach

全局重命名：
- 包名: agent_eyes → agent_reach
- CLI: agent-eyes → agent-reach
- 类名: AgentEyes → AgentReach
- 显示名: Agent Eyes → Agent Reach
- GitHub: Panniantong/agent-eyes → Panniantong/Agent-Reach

所有 36 个测试通过，CLI/doctor/read/search 全部正常。

agent_reach/channels/base.py

@@ -0,0 +1,140 @@
+# -*- coding: utf-8 -*-
+"""
+Channel base class — the universal interface for all platforms.
+
+Every channel (YouTube, Twitter, GitHub, etc.) implements this interface.
+The backend tool can be swapped anytime without changing anything else.
+
+Example:
+    class YouTubeChannel(Channel):
+        name = "youtube"
+        backends = ["yt-dlp"]  # current backend, can be swapped
+        
+        async def read(self, url, config):
+            # Just call yt-dlp, return standardized dict
+            ...
+"""
+
+import shutil
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import Any, Dict, List, Optional, Tuple
+
+
+@dataclass
+class ReadResult:
+    """Standardized read result. Every channel returns this."""
+    title: str
+    content: str
+    url: str
+    author: str = ""
+    date: str = ""
+    platform: str = ""
+    extra: dict = None
+
+    def __post_init__(self):
+        self.extra = self.extra or {}
+
+    def to_dict(self) -> dict:
+        d = {
+            "title": self.title,
+            "content": self.content,
+            "url": self.url,
+            "platform": self.platform,
+        }
+        if self.author:
+            d["author"] = self.author
+        if self.date:
+            d["date"] = self.date
+        if self.extra:
+            d["extra"] = self.extra
+        return d
+
+
+@dataclass
+class SearchResult:
+    """Standardized search result."""
+    title: str
+    url: str
+    snippet: str = ""
+    author: str = ""
+    date: str = ""
+    score: float = 0
+    extra: dict = None
+
+    def __post_init__(self):
+        self.extra = self.extra or {}
+
+    def to_dict(self) -> dict:
+        d = {
+            "title": self.title,
+            "url": self.url,
+            "snippet": self.snippet,
+        }
+        if self.author:
+            d["author"] = self.author
+        if self.date:
+            d["date"] = self.date
+        if self.extra:
+            d["extra"] = self.extra
+        return d
+
+
+class Channel(ABC):
+    """
+    Base class for all channels.
+    
+    Subclasses just need to implement:
+    - read(url, config) → ReadResult
+    - can_handle(url) → bool
+    - check(config) → (status, message)
+    
+    Optionally:
+    - search(query, config, **kwargs) → list[SearchResult]
+    """
+
+    name: str = ""                    # e.g. "youtube"
+    description: str = ""             # e.g. "YouTube video transcripts"
+    backends: List[str] = []          # e.g. ["yt-dlp"] — what external tool is used
+    requires_config: List[str] = []   # e.g. ["reddit_proxy"]
+    requires_tools: List[str] = []    # e.g. ["yt-dlp"]
+    tier: int = 0                     # 0=zero-config, 1=needs free key, 2=needs setup
+
+    @abstractmethod
+    async def read(self, url: str, config=None) -> ReadResult:
+        """Read content from a URL. Must return ReadResult."""
+        ...
+
+    @abstractmethod
+    def can_handle(self, url: str) -> bool:
+        """Check if this channel can handle this URL."""
+        ...
+
+    def check(self, config=None) -> Tuple[str, str]:
+        """
+        Check if this channel is available.
+        Returns (status, message) where status is 'ok'/'warn'/'off'/'error'.
+        """
+        # Check required tools
+        for tool in self.requires_tools:
+            if not shutil.which(tool):
+                return "off", f"需要安装：pip install {tool}"
+
+        # Check required config
+        for key in self.requires_config:
+            if config and not config.get(key):
+                return "off", f"需要配置 {key}，运行 agent-reach setup"
+
+        return "ok", f"{'、'.join(self.backends) if self.backends else '内置'}"
+
+    async def search(self, query: str, config=None, **kwargs) -> List[SearchResult]:
+        """Search this platform. Override if supported."""
+        raise NotImplementedError(f"{self.name} does not support search")
+
+    def can_search(self) -> bool:
+        """Whether this channel supports search."""
+        try:
+            # Check if search is overridden
+            return type(self).search is not Channel.search
+        except:
+            return False