Fix missing end arrowhead when a closed subpath follows an open one

Found while testing crates/pathops/src/points.rs:89-92 (Styled::arrowheads)

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/pathops/src/lib.rs

@@ -693,6 +693,29 @@ mod tests {
         assert_ne!(explicit, layer_only);
     }
 
+    #[test]
+    fn layer_end_arrow_is_drawn_when_a_closed_run_follows_the_open_one() {
+        let verts = [(0.0, 0.0), (50.0, 0.0), (0.0, 100.0), (50.0, 100.0), (25.0, 150.0)];
+        let net = VectorNetwork {
+            vertices: verts
+                .iter()
+                .enumerate()
+                .map(|(i, &(x, y))| figcraft_doc::Vertex { cap: (i == 0).then_some(StrokeCap::Round), ..figcraft_doc::Vertex::new(x, y) })
+                .collect(),
+            segments: vec![
+                figcraft_doc::Segment::line(0, 1),
+                figcraft_doc::Segment::line(2, 3),
+                figcraft_doc::Segment::line(3, 4),
+                figcraft_doc::Segment::line(4, 2),
+            ],
+            ..Default::default()
+        };
+        let path = BezPath::new();
+        let plain = StrokeProps { weight: 2.0, ..Default::default() };
+        let arrow = StrokeProps { cap_end: StrokeCap::TriangleArrow, ..plain.clone() };
+        assert_ne!(stroke_outline_of(&path, &arrow, false, Some(&net)), stroke_outline_of(&path, &plain, false, Some(&net)));
+    }
+
     #[test]
     fn equal_joins_do_not_break_closed_stroke_runs() {
         let path = sq(0.0, 0.0, 20.0);

crates/pathops/src/points.rs

@@ -86,8 +86,8 @@ impl Styled {
     /// and last end (as without point styles).
     pub(crate) fn arrowheads(&self, weight: f64, props: &StrokeProps) -> BezPath {
         let mut out = BezPath::new();
-        let last = self.runs.len().saturating_sub(1);
-        for (k, run) in self.runs.iter().enumerate().filter(|(_, r)| !r.closed) {
+        let last = self.runs.iter().filter(|r| !r.closed).count().saturating_sub(1);
+        for (k, run) in self.runs.iter().filter(|r| !r.closed).enumerate() {
             let start = self.cap_at(run.start, if k == 0 { props.cap_start } else { StrokeCap::None });
             let end = self.cap_at(run.end, if k == last { props.cap_end } else { StrokeCap::None });
             for (at_end, cap) in [(false, start), (true, end)] {