Planar source matching looks only at planes with the same normal (#917)

Body::with_planar_sources compared every planar face of a result with every unsourced planar face of its inputs, so a boolean on an import with a few thousand facets ran out of its comparison budget before it started. The lists are now sorted by normal x and each face only compares with entries inside a narrow normal window found by binary search; the exact same_support test and the work budget are unchanged. Adds an engine test joining a pin onto a 4000-sided imported prism.

crates/engine/src/tests.rs

@@ -959,6 +959,36 @@ fn step_open_then_model_on_it() {
     assert!(rel(volume(&mut s2), before) < 1e-6);
 }
 
+/// A join onto an imported body of thousands of planar faces (a converted mesh, say): each face of
+/// the result was compared with every planar face of the inputs whose source is unknown, and the
+/// join was refused past the comparison budget.
+#[test]
+fn join_onto_a_finely_faceted_import() {
+    let dir = std::env::temp_dir().join(format!("solidcraft-step-faceted-{}", std::process::id()));
+    std::fs::create_dir_all(&dir).unwrap();
+    let n = 4000;
+    let mut pts: Vec<[f64; 2]> =
+        (0..n).map(|i| std::f64::consts::TAU * f64::from(i) / f64::from(n)).map(|a| [20.0 * a.cos(), 20.0 * a.sin()]).collect();
+    pts.push(pts[0]);
+    let mut s = Session::default();
+    run(&mut s, "sketch.create", json!({"plane": "XY", "name": "P"}));
+    run(&mut s, "sketch.line", json!({"points": pts}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "solid.extrude", json!({"sketch": "P", "distance": 10}));
+    let p = dir.join("Faceted.step");
+    run(&mut s, "file.export", json!({"path": p.to_string_lossy()}));
+    let prism = volume(&mut s);
+
+    let mut d = Session::default();
+    run(&mut d, "file.insert_step", json!({"path": p.to_string_lossy()}));
+    run(&mut d, "sketch.create", json!({"plane": "XY", "name": "Pin"}));
+    run(&mut d, "sketch.rectangle.two_point", json!({"p0": [-5, -5], "p1": [5, 5]}));
+    run(&mut d, "sketch.finish", json!({}));
+    run(&mut d, "solid.extrude", json!({"sketch": "Pin", "distance": 25, "operation": "join"}));
+    assert_eq!(d.model.state().bodies.len(), 1);
+    assert!(rel(volume(&mut d), prism + 10.0 * 10.0 * 15.0) < 1e-6, "{}", volume(&mut d));
+}
+
 /// Shell an imported body; insert STEP into an existing design; extension case; bad files.
 #[test]
 fn step_insert_shell_and_errors() {