feat(channels): add Toutiao channel with search and read (#229)

Zero-config channel (tier=0). Searches so.toutiao.com by scraping
embedded JSON from script tags. Fixes URL extraction order from PR #207
(article_url is the primary field, not display.info.url). Adds read()
via Jina Reader. 89 tests passing.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_toutiao_channel.py

@@ -0,0 +1,117 @@
+# -*- coding: utf-8 -*-
+"""Tests for ToutiaoChannel."""
+
+import json
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from agent_reach.channels.toutiao import ToutiaoChannel, _parse_search_results
+
+
+@pytest.fixture
+def ch():
+    return ToutiaoChannel()
+
+
+class TestToutiaoChannelAttributes:
+    def test_name(self, ch):
+        assert ch.name == "toutiao"
+
+    def test_tier(self, ch):
+        assert ch.tier == 0
+
+    def test_backends(self, ch):
+        assert ch.backends
+
+
+class TestToutiaoCanHandle:
+    def test_matches_toutiao(self, ch):
+        assert ch.can_handle("https://www.toutiao.com/article/123")
+
+    def test_matches_search(self, ch):
+        assert ch.can_handle("https://so.toutiao.com/search?keyword=ai")
+
+    def test_rejects_other(self, ch):
+        assert not ch.can_handle("https://www.baidu.com")
+
+
+class TestToutiaoCheck:
+    def test_check_ok(self, ch):
+        mock_resp = MagicMock()
+        mock_resp.__enter__ = lambda s: s
+        mock_resp.__exit__ = MagicMock(return_value=False)
+        mock_resp.status = 200
+        mock_resp.read.return_value = b'{"data": {"title": "test"}}'
+        with patch("urllib.request.urlopen", return_value=mock_resp):
+            status, msg = ch.check()
+        assert status == "ok"
+
+    def test_check_exception(self, ch):
+        with patch("urllib.request.urlopen", side_effect=Exception("timeout")):
+            status, msg = ch.check()
+        assert status == "warn"
+        assert "timeout" in msg
+
+
+class TestParseSearchResults:
+    def _make_script(self, data: dict) -> str:
+        # Production code skips scripts < 1000 chars; pad to exceed threshold
+        payload = json.dumps({"data": data})
+        padding = "x" * max(0, 1001 - len(payload))
+        padded = payload[:-1] + f',"_pad":"{padding}"' + payload[-1]
+        return f'<script type="text/javascript">{padded}</script>'
+
+    def test_extracts_article_url_first(self):
+        html = self._make_script({
+            "title": "测试文章",
+            "article_url": "https://www.toutiao.com/article/1",
+            "template_key": "undefined-default",
+        })
+        results = _parse_search_results(html)
+        assert len(results) == 1
+        assert results[0]["url"] == "https://www.toutiao.com/article/1"
+        assert results[0]["title"] == "测试文章"
+
+    def test_fallback_to_source_url(self):
+        html = self._make_script({
+            "title": "备用 URL 文章",
+            "source_url": "https://www.toutiao.com/source/1",
+            "template_key": "undefined-default",
+        })
+        results = _parse_search_results(html)
+        assert len(results) == 1
+        assert results[0]["url"] == "https://www.toutiao.com/source/1"
+
+    def test_skips_entries_without_url(self):
+        html = self._make_script({
+            "title": "无 URL 文章",
+            "template_key": "undefined-default",
+        })
+        results = _parse_search_results(html)
+        assert results == []
+
+    def test_skips_entries_without_title(self):
+        html = self._make_script({
+            "article_url": "https://www.toutiao.com/article/1",
+            "template_key": "undefined-default",
+        })
+        results = _parse_search_results(html)
+        assert results == []
+
+    def test_skips_skip_templates(self):
+        html = self._make_script({
+            "title": "广告",
+            "article_url": "https://www.toutiao.com/article/1",
+            "template_key": "Bottom-ad",
+        })
+        results = _parse_search_results(html)
+        assert results == []
+
+    def test_empty_html(self):
+        assert _parse_search_results("") == []
+
+    def test_short_scripts_ignored(self):
+        # script < 1000 chars should be skipped
+        html = '<script>{"data": {"title": "x", "article_url": "y"}}</script>'
+        assert _parse_search_results(html) == []