rtx-cfd: overset Schwarz stall rule guarded (fires only within 10× the tolerance) — unguarded it cut CFD1's transient at round 3 every step and the coupled march diverged at ny=62 (pressure 4e4 → 1e140 by step 450); CFD1 harness knobs (stall, step cap, trace)

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2

crates/specialized/rtx-cfd/src/solvers/incompressible/overset/mod.rs

@@ -716,7 +716,17 @@ impl OversetPisoSolver {
                 // 20-round cap at n = 64, and a 7.5 h n = 128 march.
                 history.push(change);
                 let k = self.params.stall_rounds;
-                if k > 0 && history.len() > k && change > 0.7 * history[history.len() - 1 - k] {
+                // Guarded: a stall counts only once the exchange is already
+                // within 10× the tolerance — Anderson converges
+                // non-monotonically, and an unguarded 30%-over-k-rounds test
+                // fired at round 3 of the first corrector throughout CFD1's
+                // transient, under-converging every step until the coupled
+                // march diverged (pressure 4e4 → 1e140 by step 450 at ny = 62).
+                if k > 0
+                    && history.len() > k
+                    && change > 0.7 * history[history.len() - 1 - k]
+                    && change <= 10.0 * self.params.schwarz_tolerance * scale
+                {
                     schwarz_stalled += 1;
                     done = true;
                     break;