Boundary Fill (SurfaceSculpt): solids from the cells tool bodies enclose (inside some tools, outside the rest), each picked by a point, as new bodies or joined/cut/intersected, tools optionally removed

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

crates/engine/src/tests.rs

@@ -1808,3 +1808,20 @@ fn align_with_snap_points() {
     assert!((min(0) - 20.0).abs() < 1e-6 && (min(1) - 20.0).abs() < 1e-6 && (min(2) - 10.0).abs() < 1e-6, "{m}");
     assert!(s.execute("solid.align", &json!({"bodies": ["Cube"], "from": {"snap": "nope", "at": [0, 0, 0]}, "to": [0, 0, 0]})).is_err());
 }
+
+/// Boundary Fill: the lens two overlapping boxes share, and one box less the other.
+#[test]
+fn boundary_fill_cells() {
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 20, "width": 20, "height": 20, "body_name": "A"}));
+    run(&mut s, "solid.box", json!({"corner": [10, 0, 0], "length": 20, "width": 20, "height": 20, "body_name": "B"}));
+    let r = run(&mut s, "SurfaceSculpt", json!({"tools": ["A", "B"], "cells": [[15, 10, 10]], "remove_tools": true}));
+    let m = run(&mut s, "inspect.measure", json!({}));
+    assert_eq!(m["body_count"], 1, "{r} {m}");
+    assert!(rel(m["total"]["volume_mm3"].as_f64().unwrap_or(0.0), 10.0 * 20.0 * 20.0) < 1e-9);
+    run(&mut s, "edit.undo", json!({}));
+    run(&mut s, "SurfaceSculpt", json!({"tools": ["A", "B"], "cells": [[5, 10, 10], [25, 10, 10]], "remove_tools": true}));
+    let m = run(&mut s, "inspect.measure", json!({}));
+    assert!(rel(m["total"]["volume_mm3"].as_f64().unwrap_or(0.0), 2.0 * 10.0 * 20.0 * 20.0) < 1e-9, "{m}");
+    assert!(s.execute("SurfaceSculpt", &json!({"tools": ["A"], "cells": [[100, 100, 100]]})).is_err());
+}