feat: parallelize lookup (Wiki+SearXNG) and include Wikipedia thumbnails

Runs the Wikipedia summary and SearXNG search concurrently and returns
both when available, so current-event questions aren't masked by a
generic role article from Wikipedia. When the Wikipedia summary includes
a thumbnail, it is cached through the existing image pipeline and
surfaced as an embeddable markdown snippet alongside the extract.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_wikipedia.py

@@ -37,6 +37,33 @@ async def test_wiki_summary_returns_extract():
     assert result["title"] == "Python (programming language)"
     assert "Python" in result["extract"]
     assert result["url"].startswith("https://")
+    assert result["thumbnail_url"] == ""
+
+
+@pytest.mark.asyncio
+async def test_wiki_summary_includes_thumbnail():
+    """Thumbnail URL is extracted when the article has an image."""
+    payload = {
+        "type": "standard",
+        "title": "Hedgehog",
+        "extract": "Hedgehogs are spiny mammals.",
+        "content_urls": {"desktop": {"page": "https://en.wikipedia.org/wiki/Hedgehog"}},
+        "thumbnail": {"source": "https://upload.wikimedia.org/foo-320px.jpg"},
+        "originalimage": {"source": "https://upload.wikimedia.org/foo.jpg"},
+    }
+    mock_resp = _make_mock_response(payload)
+
+    with patch("fabledassistant.services.wikipedia.httpx.AsyncClient") as mock_client_cls:
+        mock_client = AsyncMock()
+        mock_client.__aenter__ = AsyncMock(return_value=mock_client)
+        mock_client.__aexit__ = AsyncMock(return_value=False)
+        mock_client.get = AsyncMock(return_value=mock_resp)
+        mock_client_cls.return_value = mock_client
+
+        result = await wiki_summary("Hedgehog")
+
+    assert result is not None
+    assert result["thumbnail_url"] == "https://upload.wikimedia.org/foo-320px.jpg"
 
 
 @pytest.mark.asyncio