fsi2 harness: RTX_FSI2O_BG_CONVECTION knob (tvd default / upwind) on the background, printed in both headers beside the patch's — the patch scheme was excluded as the h-term's carrier (upwind ladder +1.52 vs TVD +1.73 W/m from ny 41 to 62), the background's wake dissipation is the registered next probe

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LzcjQX7tvgn87CQCyg9Cfr

crates/specialized/rtx-fsi/tests/fsi2_harness/overset_march.rs

@@ -100,7 +100,7 @@ pub fn run_march_overset(case: BenchmarkCase, config: &OversetMarchConfig) -> Ov
     // Every setting the acceptance rule reads, printed once: P5-3 lost a
     // day to a floor of 2e-4 against the overnight marches' 1e-6.
     println!(
-        "  coupling: {} (reuse {}, ω0 {}, c1 {}), floor {:.1e}, rtol {:.1e}, stall accept {:.1e}, max subit {}, predictor {}, s = {}, patch offset {} h × {} rows, patch convection {:?}",
+        "  coupling: {} (reuse {}, ω0 {}, c1 {}), floor {:.1e}, rtol {:.1e}, stall accept {:.1e}, max subit {}, predictor {}, s = {}, patch offset {} h × {} rows, patch convection {:?}, bg convection {:?}",
         cfg.coupler,
         cfg.reuse,
         cfg.initial_relaxation,
@@ -114,6 +114,7 @@ pub fn run_march_overset(case: BenchmarkCase, config: &OversetMarchConfig) -> Ov
         std::env::var("RTX_FSI2O_PATCH_OFFSET").unwrap_or_else(|_| "6".into()),
         std::env::var("RTX_FSI2O_PATCH_ROWS").unwrap_or_else(|_| "12".into()),
         super::overset::patch_convection(),
+        super::overset::bg_convection(),
     );
 
     // Phase 1: rigid flag to t_release (`RTX_FSI2O_LOAD=dir` replaces the