v2.0.0 — Pure glue architecture: zero copied code, pluggable channels

BREAKING: Complete architectural rewrite.

Before: Copied x-reader's fetcher code into readers/ (1205 lines of borrowed code)
After: Pluggable channel system where each channel is a thin wrapper (~50 lines)
       around the best external tool for that platform. Zero copied code.

Architecture:
- channels/base.py — Universal Channel interface (read, search, check)
- channels/web.py — Jina Reader API (swappable)
- channels/github.py — GitHub API (swappable)
- channels/twitter.py — birdx + Jina fallback (swappable)
- channels/youtube.py — yt-dlp (swappable)
- channels/reddit.py — Reddit JSON API + proxy (swappable)
- channels/rss.py — feedparser (swappable)
- channels/bilibili.py — Bilibili API (swappable)
- channels/exa_search.py — Exa semantic search (swappable)

Key design: every backend can be swapped by changing ONE file.
YouTube dies? Change youtube.py. Exa sucks? Swap exa_search.py for Tavily.
Nothing else changes.

Removed: reader.py, schema.py, readers/, search/, utils/ (all x-reader code)
Tests: 36/36 passing

agent_eyes/channels/__init__.py

@@ -0,0 +1,67 @@
+# -*- coding: utf-8 -*-
+"""
+Channel registry — routes URLs to the right channel.
+
+This is the core of Agent Eyes' pluggable architecture.
+Add a new channel: just create a file and register it here.
+Swap a backend: just change the implementation inside the channel file.
+"""
+
+from typing import Dict, List, Optional
+from .base import Channel, ReadResult, SearchResult
+
+# Import all channels
+from .web import WebChannel
+from .github import GitHubChannel
+from .twitter import TwitterChannel
+from .youtube import YouTubeChannel
+from .reddit import RedditChannel
+from .rss import RSSChannel
+from .bilibili import BilibiliChannel
+from .exa_search import ExaSearchChannel
+
+
+# Channel registry — order matters (first match wins, web is last as fallback)
+ALL_CHANNELS: List[Channel] = [
+    GitHubChannel(),
+    TwitterChannel(),
+    YouTubeChannel(),
+    RedditChannel(),
+    BilibiliChannel(),
+    RSSChannel(),
+    ExaSearchChannel(),
+    WebChannel(),        # Fallback — handles any URL
+]
+
+# Search-capable channels
+SEARCH_CHANNELS: Dict[str, Channel] = {
+    ch.name: ch for ch in ALL_CHANNELS if ch.can_search()
+}
+
+
+def get_channel_for_url(url: str) -> Channel:
+    """Find the right channel for a URL."""
+    for channel in ALL_CHANNELS:
+        if channel.can_handle(url):
+            return channel
+    return WebChannel()  # Should never reach here, but just in case
+
+
+def get_channel(name: str) -> Optional[Channel]:
+    """Get a channel by name."""
+    for ch in ALL_CHANNELS:
+        if ch.name == name:
+            return ch
+    return None
+
+
+def get_all_channels() -> List[Channel]:
+    """Get all registered channels."""
+    return ALL_CHANNELS
+
+
+__all__ = [
+    "Channel", "ReadResult", "SearchResult",
+    "ALL_CHANNELS", "SEARCH_CHANNELS",
+    "get_channel_for_url", "get_channel", "get_all_channels",
+]