Using text editor apps through Files.App integration doesn’t truncate files on edits

### Checklist

- [x] Using latest version on the [App Store](http://itunes.apple.com/app/id1156707581)
- [x] Read the [docs](http://blink.sh/docs/)
- [x] Searched for [existing GitHub issues](https://github.com/blinksh/blink/issues)

### Configuration

Blink Version 17.0.1.840
iPadOS Versions 17.0 (21A329)

### Describe the bug

When using a separate text editor app to edit remote files through Blink’s Files.App integration, files are not shortened on edits that reduce their length.

For example, a plaintext file containing “abcd”, if opened in a text editor app through Blink’s file integration and shortened to “cd”, would appear on the server as “cdcd”. These extra remaining characters are not visible on the local version of the file or in the text editor. Expected behavior is that the remote file would match the local version.

I tested this with files hosted on a unix server setup in Blink with ssh keys into a non-root account, with Files.App integration into its home directory. I’ve reproduced this using the text editor apps Runestone, Subtext, and QuickText.

The issue names Blink’s Files.App integration and reproductions with Runestone, Subtext, and QuickText, but no source files or tests. First reproduce an edit that shortens a remote file, then trace the Files.App integration’s write path; done means the remote file exactly matches the shortened local content without leftover characters.

Written by the indexing model from the issue text.