[BUG] Correction overlay overflows out of Textedit window

## Description
When using Harper in TextEdit, the corrections (squiggly lines, etc.) overflow out of TextEdit window into the rest of the workspace.

## To Reproduce
Steps to reproduce the behavior:
1. Install Harper on Macos
2. Follow the "Getting Started" guide till the launch of TextEdit
3. Open a file longer than the viewing port containing spelling errors
4. See error

## Expected behavior
The corrections should only be displayed on the visible portion of the text.

## Screenshots

## Platform
MacBook Pro
13-inch, M1, 2020

Chip Apple M1
Memory 8 GB
Startup disk Macintosh HD
Serial number C02FDGFBQ05D

macOS 26.5.2 (25F84)

Reproduce the overflow using the Harper Getting Started guide, TextEdit, and a document longer than the viewing port with spelling errors on macOS. Investigate the TextEdit integration and verify that correction markings remain confined to the visible portion of the TextEdit window.

Written by the indexing model from the issue text.