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

src/timmy/session.py

@@ -31,7 +31,7 @@ _TOOL_CALL_JSON = re.compile(
 
 # Matches function-call-style text: memory_search(query="...") etc.
 _FUNC_CALL_TEXT = re.compile(
-    r"\b(?:memory_search|web_search|shell|python|read_file|write_file|list_files|calculator)"
+    r"\b(?:memory_search|shell|python|read_file|write_file|list_files|calculator)"
     r"\s*\([^)]*\)",
 )