fix(track-changes): tighten setNodeMarkup heuristic and fix toggleLinkedStyle cursor handling

- Add step.insert === 1 check to exclude lift() false positives
- Add map.appendMap() for consistency with other step handlers
- Fix nodeAt() null-return by always falling back to findParentNodeClosestToPos
- Update stale test to reflect new cursor selection behavior

Author: caio-pizzol

packages/super-editor/src/extensions/linked-styles/linked-styles.js

@@ -68,7 +68,7 @@ export const LinkedStyles = Extension.create({
         const { tr } = params;
         let node = tr.doc.nodeAt(tr.selection.$from.pos);
 
-        if (node && node.type.name !== 'paragraph') {
+        if (!node || node.type.name !== 'paragraph') {
           node = findParentNodeClosestToPos(tr.selection.$from, (n) => {
             return n.type.name === 'paragraph';
           })?.node;

packages/super-editor/src/extensions/linked-styles/linked-styles.test.js

@@ -135,13 +135,13 @@ describe('LinkedStyles Extension', () => {
     });
 
     describe('toggleLinkedStyle', () => {
-      it('should return false for an empty selection', () => {
+      it('should apply style with a cursor (empty) selection', () => {
         setParagraphCursor(editor.view, 0); // Cursor selection at first paragraph
         const result = editor.commands.toggleLinkedStyle(headingStyle, 'paragraph');
 
-        expect(result).toBe(false);
+        expect(result).toBe(true);
         const firstParagraph = findParagraphInfo(editor.state.doc, 0);
-        expect(getParagraphProps(firstParagraph.node).styleId).toBeUndefined();
+        expect(getParagraphProps(firstParagraph.node).styleId).toBe('Heading1');
       });
 
       it('should apply style when no style is currently set', () => {

packages/super-editor/src/extensions/track-changes/trackChangesHelpers/replaceAroundStep.js

@@ -97,10 +97,13 @@ export const replaceAroundStep = ({
   // Detect setNodeMarkup steps: they preserve the node type and content,
   // only changing attributes (e.g. paragraph styleId for heading changes).
   // These are safe to apply — they don't alter document structure.
-  const isNodeMarkupChange = step.structure && step.gapFrom === step.from + 1 && step.gapTo === step.to - 1;
+  // We also check step.insert === 1 to exclude lift() operations (insert === 0).
+  const isNodeMarkupChange =
+    step.structure && step.insert === 1 && step.gapFrom === step.from + 1 && step.gapTo === step.to - 1;
 
   if (isNodeMarkupChange) {
     newTr.step(step);
+    map.appendMap(step.getMap());
     return;
   }