fix: prune dead web_search tool — ddgs never installed (#87)

Remove DuckDuckGoTools import, all web_search registrations across 4 toolkit
factories, catalog entry, safety classification, prompt references, and
session regex. Total: -41 lines of dead code.

consult_grok is functional (grok_enabled=True, API key set) and opt-in,
so it stays — but Timmy never calls it autonomously, which is correct
sovereign behavior (no cloud calls unless user permits).

Closes #87

tests/integrations/test_discord_confirmation.py

@@ -69,7 +69,7 @@ class TestGetImpactLevel:
     def test_low_impact(self):
         from integrations.chat_bridge.vendors.discord import _get_impact_level
 
-        assert _get_impact_level("web_search") == "low"
+        assert _get_impact_level("calculator") == "low"
         assert _get_impact_level("unknown") == "low"
 
 
@@ -104,10 +104,10 @@ class TestToolSafety:
 
         assert requires_confirmation("calculator") is False
 
-    def test_web_search_is_safe(self):
+    def test_memory_search_is_safe(self):
         from timmy.tool_safety import requires_confirmation
 
-        assert requires_confirmation("web_search") is False
+        assert requires_confirmation("memory_search") is False
 
     def test_unknown_tool_requires_confirmation(self):
         from timmy.tool_safety import requires_confirmation