review: update stale duckduckgo-search references to ddgs

tests/test_web_search.py

@@ -84,7 +84,7 @@ class TestTavilyClient:
 
 class TestDuckDuckGoClient:
     def test_integration_via_mock_ddgs(self):
-        """Patch the duckduckgo_search import inside DuckDuckGoClient.search."""
+        """Patch the ddgs import inside DuckDuckGoClient.search."""
         mock_ddgs = MagicMock()
         mock_ddgs.__enter__ = MagicMock(return_value=mock_ddgs)
         mock_ddgs.__exit__ = MagicMock(return_value=False)

turnstone/core/session.py

@@ -2803,7 +2803,7 @@ class ChatSession:
                 "needs_approval": False,
                 "error": (
                     "Error: No web search backend available. "
-                    "Install duckduckgo-search (`pip install duckduckgo-search`), "
+                    "Install the ddg extra (`pip install turnstone[ddg]`), "
                     "configure a Tavily API key, or set tools.web_search_backend."
                 ),
             }

turnstone/core/web_search.py

@@ -3,7 +3,7 @@
 ``web_search`` is an abstract capability with swappable clients:
 
 * **TavilyClient** — paid, high quality, requires API key
-* **DuckDuckGoClient** — free, no API key, uses ``duckduckgo-search``
+* **DuckDuckGoClient** — free, no API key, uses ``ddgs``
 
 Auto-detection (default): Tavily if key present, else DDG if installed,
 else ``None`` (tool removed from tool list).