M4.33: Export As with Use Artboards (All or a range) and art bounds

File > Export > Export As... (file.exportAs) picks any writable format and Use Artboards: All
or a range writes one file per artboard, <file>-<artboard>.<ext> (a PDF keeps them as pages);
off, the export covers the bounds of the visible art (an artless document is refused before the
save dialog). The format's options dialog follows: PNG/JPEG/WebP Options, SVG Options, or Save
PDF for artboards as pages. document.export takes useArtboards for raster formats (true: one
file per chosen artboard, default all) and PDF (false: the art's bounds), and the app's exports
return every file written and the encoder's warnings.

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

crates/render/src/encode/tests.rs

@@ -171,3 +171,21 @@ fn anti_alias_none_is_the_same_on_every_thread_count() {
     let worst = st.pixels.iter().zip(&mt.pixels).map(|(a, b)| a.abs_diff(*b)).max().unwrap();
     assert!(worst <= 4, "max channel difference {worst}");
 }
+
+#[test]
+fn art_bounds_cover_visible_art_only() {
+    let mut d = circle_doc();
+    let l = d.layers[0].id;
+    let hidden = {
+        let id = d.alloc_id();
+        let mut n =
+            Node::path(id, shapes::rectangle(Rect::new(100.0, 100.0, 120.0, 120.0)), Appearance::basic(Paint::solid(Color::BLACK), Paint::None, 0.0));
+        n.visible = false;
+        n
+    };
+    d.insert(Some(l), 1, hidden).unwrap();
+    let b = art_bounds(&d).unwrap();
+    assert!((b.x0 - 5.3).abs() < 1e-6 && (b.x1 - 31.1).abs() < 1e-6 && (b.y1 - 26.2).abs() < 1e-6, "{b:?}");
+    let empty = Document::new(10.0, 10.0);
+    assert_eq!(art_bounds(&empty), None);
+}