No panics in the boolean's final assembly (the web build aborts on any panic: the Plastic Enclosure sample panicked 8 times and crashed the browser's start page); face pushes check their result and fall back to the general offset (a boss standing on a plate joins again with off-axis cylinder seams); offset errors name the face they can't move; docs/robustness.md with the before and after rates; caught panics counted per design in the robustness runs

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/kernel/src/splitface.rs

@@ -1230,7 +1230,8 @@ mod tests {
         let mut tops: Vec<f64> = s.faces(0.01).unwrap().iter().filter(|f| (f.centroid.z - 20.0).abs() < 1e-6).map(|f| f.area).collect();
         tops.sort_by(f64::total_cmp);
         let pi = std::f64::consts::PI;
-        assert!(rel(tops[0], pi * 16.0) < 1e-3 && rel(tops[1], pi * 84.0) < 1e-3, "{tops:?}");
+        // (Face areas come from meshes: within their sag, which depends on where seams lie.)
+        assert!(rel(tops[0], pi * 16.0) < 2e-3 && rel(tops[1], pi * 84.0) < 2e-3, "{tops:?}");
     }
 
     /// A plane through a hole in a plate's top: the top splits in two, each piece holding