decide tests: the rotation margin arithmetic is a compile-time assertion in self_run.rs, not a runtime one

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

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

@@ -260,8 +260,6 @@ fn the_ladder_ends_before_the_cap_whenever_the_flush_was_written() {
             assert!(finished.is_some_and(|end| end < cap as i64), "flush at {second}: ended at {finished:?}, cap {cap}");
         }
     }
-    // The rotation margin leaves room: this is the arithmetic the const assertion pins.
-    assert!(GRACE + LADDER_S < ROTATE_MARGIN_S);
 }
 
 #[test]