decide tests: pin the ladder allowance the cap clamp depends on (mutants on LADDER_S survived)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/mind-body/src/self_run/decide/tests.rs

@@ -453,3 +453,10 @@ fn enumerate(length: usize, symbols: &mut Vec<Sym>) {
 fn every_order_of_up_to_four_events_keeps_the_write_accounting_and_the_single_flush() {
     enumerate(4, &mut Vec::new());
 }
+
+#[test]
+fn the_ladder_allowance_is_three_escalations_the_drain_and_a_minute() {
+    // The sweep above is only as long as this constant: pin the number the spec derives (3 * 120 + 2 + 60).
+    assert_eq!(LADDER_S, 422);
+    assert!(LADDER_S >= 3 * ESC + EXIT_DRAIN_S, "the allowance covers the ladder it is named for");
+}