Write some helper methods rather than directly adding transformations to the list

This is hard to read and confusing:

    vimState.recordedState.transformations.push({
      type    : "insertText",
      text    : textToAdd,
      position: position,
      diff    : new PositionDiff(0, -1),
    });

This is easy to read and not confusing:

    vimState = TextEditor.insert(vimState, textToAdd, position, new PositionDiff(0, -1));

I don't know why it took me so long to come up with this idea! It's much better than my current solution.

The issue names no files, tests, or entry points; start by locating direct transformations matching the shown vimState.recordedState.transformations.push pattern. Refactor those operations behind readable helper methods such as TextEditor.insert, then verify that the affected behavior remains unchanged.