#1063: a fill chosen with characters selected colours just them

Choosing a fill or stroke (Color panel, Swatches, the proxies) while the
Type tool had a few characters selected painted every run of the type
object. As in Illustrator, it now goes to the selected characters only:
the runs are split at the selection's ends and the paint is placed on
the runs in between, as one undo step; a stroke gets a 1 pt weight
where it had none. With only a caret, or with explicit ids or an item,
paint.setFill/setStroke behave as before.

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

crates/engine/src/tests_textedit.rs

@@ -563,3 +563,35 @@ fn automatic_alignment_updates_during_edits_and_can_be_overridden() {
     legacy["para"]["justify"] = json!("Left");
     assert_eq!(serde_json::from_value::<TextObject>(legacy).unwrap().para.justify, vectorcraft_doc::Justify::Left);
 }
+
+/// #1063: a fill (or stroke) chosen while the Type tool has characters selected colours just
+/// those characters, as one undo step; the rest of the type keeps its colour.
+#[test]
+fn a_fill_chosen_with_characters_selected_colours_only_them() {
+    let mut s = session();
+    let v = ViewInfo::default();
+    s.select_tool("type", v).unwrap();
+    click(&mut s, 50.0, 300.0);
+    let id = s.doc().unwrap().selection.objects[0];
+    s.tool_text("Sample Text", v).unwrap();
+    let before = obj(&s, id).runs[0].style.fill.clone();
+    s.set_tool_option("select", &json!({"start": 0, "end": 6}));
+    s.execute("paint.setFill", &json!({"color": "#00a000"})).unwrap();
+    let t = obj(&s, id);
+    assert_eq!(t.runs.len(), 2);
+    assert_eq!(t.runs[0].text, "Sample");
+    assert_eq!(t.runs[0].style.fill, Paint::solid(vectorcraft_color::Color::rgb8(0, 160, 0)));
+    assert_eq!(t.runs[1].text, " Text");
+    assert_eq!(t.runs[1].style.fill, before);
+    // A stroke goes on the selected characters only, with a weight to show.
+    s.execute("paint.setStroke", &json!({"color": "#ff0000"})).unwrap();
+    let t = obj(&s, id);
+    assert!(t.runs[0].style.stroke_width > 0.0 && !t.runs[0].style.stroke.is_none());
+    assert!(t.runs[1].style.stroke.is_none());
+    // One undo step each.
+    let labels = undo_labels(&s);
+    assert_eq!(&labels[labels.len() - 2..], ["Fill Color", "Stroke Color"]);
+    s.execute("edit.undo", &json!({})).unwrap();
+    s.execute("edit.undo", &json!({})).unwrap();
+    assert!(obj(&s, id).runs.iter().all(|r| r.style.fill == before));
+}