fix: record the calling client and only schema-known names in audit entries (SEC-12, SEC-18)

tests/test_server.py

@@ -354,9 +354,9 @@ async def test_unknown_tool_is_a_protocol_error_and_is_audited() -> None:
             await client.call_tool("gitea_does_not_exist", {"a": 1})
 
     assert caught.value.code == -32602
-    assert "gitea_does_not_exist" in caught.value.message
+    assert "gitea_does_not_exist" not in caught.value.message
     entry = audit_entries()[-1]
-    assert entry["tool_name"] == "gitea_does_not_exist"
+    assert entry["tool_name"] == "(unknown tool, 20 chars)"
     assert entry["outcome"] == "unknown_tool"