fix: axis or tangent plane on a drill tip no longer fails with "no face at NaN" (#567) (#655)

The nearest point on a triangle with a zero-length edge (a cone's tip) is no longer NaN, so an axis or tangent plane on a drill tip works again (#567).

crates/doc/src/name_lookup.rs

@@ -104,7 +104,8 @@ fn nearest_on_face(m: &Mesh, face: usize, p: Vec3) -> Option<(f64, Vec3)> {
         let Some([a, b, c]) = m.tri(t) else { continue };
         let q = closest(p, a, b, c);
         let d = q.dist(p);
-        if best.is_none_or(|x| d < x.0) {
+        // A non-finite candidate must never become the best: nothing compares less than NaN.
+        if d.is_finite() && best.is_none_or(|x| d < x.0) {
             best = Some((d, q));
         }
     }
@@ -317,7 +318,7 @@ fn legacy_locate<'a>(bodies: impl Iterator<Item = (usize, &'a ModelBody)>, name:
             let Some([a, bb, c]) = m.tri(t) else { continue };
             let q = closest(p, a, bb, c);
             let d = q.dist(p) - if exact { 1e-9 } else { 0.0 };
-            if best.is_none_or(|x| d < x.0) {
+            if d.is_finite() && best.is_none_or(|x| d < x.0) {
                 best = Some((d, bi, *f as usize, q, !exact, tol));
             }
         }