docs(graph): validation warns at start-up, there is no --validate flag

Graph-Agents.md

@@ -160,7 +160,8 @@ nodes:
   `timeout`s on `llm` nodes (which *do* route via `fallback`) as the
   operative bound, and treat the graph-level `timeout` as a generous
   backstop. `0` disables the bound entirely (equivalent to unset;
-  `--validate` flags the explicit `0` as an intentional choice). For graphs
+  the validator warns on the explicit `0` at start-up so the choice is
+  visible). For graphs
   that must run until they complete, e.g. an end-to-end implementation run;
   pair it with a sane `max_loop_iterations`. **Bounds compose outward-in:**
   if this graph is run by another graph's `agent` node, that node's