M8: points moved by one offset still carry the regions' paint frames

Setting each point's own coordinate moved the points one at a time, so when every point of a layer moved by the same offset (`{"x": {"add": 10}}` on all of them) `ops::move_vertices` no longer saw the whole network move and left the regions' paint frames behind. Points with the same offset now move together.

Verified: `moving_every_point_by_one_offset_carries_the_regions_paint_frame` failed before this and passes; vectoredit tests 92 passed, junk sweep 49 passed, clippy and fmt clean.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Model-Effort: Opus 5.5 drove and wrote

crates/engine/src/canvas/vectoredit.rs

@@ -1017,9 +1017,18 @@ pub fn specs() -> Vec<CommandSpec> {
                 if moves.is_empty() {
                     return Err(bad("vector.edit.position", "select points"));
                 }
+                // Points with the same offset move together, so moving every point by one offset
+                // still carries the regions' paint frames, as a drag of all of them does.
+                let mut groups: Vec<(Vec2, Vec<usize>)> = Vec::new();
+                for (i, d) in moves {
+                    match groups.iter_mut().find(|(g, _)| (*g - d).hypot() < 1e-9) {
+                        Some((_, v)) => v.push(i),
+                        None => groups.push((d, vec![i])),
+                    }
+                }
                 edit(s.doc_mut()?, ve.id, |net| {
-                    for (i, d) in &moves {
-                        ops::move_vertices(net, &[*i], *d);
+                    for (d, v) in &groups {
+                        ops::move_vertices(net, v, *d);
                     }
                 })?;
                 Ok(json!({"ok": true}))

crates/engine/src/canvas/vectoredit/position_tests.rs

@@ -100,6 +100,32 @@ fn the_values_are_in_the_parents_coordinates() {
     assert!(near(after[0].1, before[0].1));
 }
 
+#[test]
+fn moving_every_point_by_one_offset_carries_the_regions_paint_frame() {
+    // `{add}` on every point is a plain translation: the region's paint frame goes with the
+    // points, as when they are dragged together.
+    let mut s = Session::new();
+    let id = rect(&mut s);
+    {
+        let node = s.doc_mut().unwrap().get_mut(id).unwrap();
+        let NodeKind::Vector { network } = &mut node.kind else { panic!("expected a vector") };
+        assert!(!network.regions.is_empty(), "the rectangle has a region");
+        for region in &mut network.regions {
+            region.paint_space = Some(figcraft_doc::RegionPaintSpace { width: 100.0, height: 100.0, transform: Affine::IDENTITY });
+        }
+    }
+    let frame = |s: &Session| {
+        let world = s.doc().unwrap().world_transform(id);
+        world * net(s, id).regions[0].paint_space.as_ref().unwrap().transform
+    };
+    let before = frame(&s);
+    let all: Vec<usize> = (0..net(&s, id).vertices.len()).collect();
+    ex(&mut s, "vector.edit.select", json!({"vertices": all}));
+    ex(&mut s, "vector.edit.position", json!({"x": {"add": 10}}));
+    let (want, got) = ((Affine::translate((10.0, 0.0)) * before).as_coeffs(), frame(&s).as_coeffs());
+    assert!(want.iter().zip(got).all(|(a, b)| near(*a, b)), "{got:?} vs {want:?}");
+}
+
 #[test]
 fn junk_is_refused_and_changes_nothing() {
     let mut s = Session::new();