Clarify frozen endpoint scope and gravity target interpretation

experiments/NONLINEAR_STEP_INVESTIGATION_2026-09-18.md

@@ -43,10 +43,19 @@ all 31 auxiliary gravity solves passed, but the final nonlinear residual was
 1/512. Every trial prepared successfully; all nineteen rejections were
 residual-decrease failures, and geometry never limited the step.
 
+That campaign did not retain every raw Newton direction. The new late-state
+probe computes a fresh direction at its saved final endpoint; it does not
+claim to replay the preceding iteration's rejected trials. A plateau in a
+bounded twelve-step run is also not proof that all subsequent steps must
+fail. The fresh trial measurements can test that possibility.
+
 The final squared-residual shares are approximately 42.42% hydrostatic,
 26.23% closure, 15.87% surface, 10.43% gravity, and 5.05% mass. This motivates
 examining retained-equation curvature after the gravity correction, rather
 than assuming the earlier gravity or pressure-preparation failure persists.
+The last auxiliary prepared defect, approximately 3.33e-14, measures agreement
+with the affine gravity target, not satisfaction of the gravity equations.
+The final gravity-block residual norm is approximately 4.51e-6.
 
 Keep the complete physical equations, fixed normalization, optional
 central-density specification (absent here), mesh, and acceptance thresholds