Do not reload text document if text was apened out-of-band?

[krassowski]

Problem

Reading files with logs when using jupyter-collaboration or jupyter-server-documents is difficult because the cursor, selection, and to some degree scroll position jumps back to the top as the logs get appended, e.g. with:

import time
for i in range(100_000):
    !echo "log {i}" >> logs.txt
    time.sleep(0.01)

Screencast.From.2025-11-26.13-49-23.mp4

Proposed Solution

Attempt to emit granular edits for changes to text file which are not complete rewrites even if the coarse set method is used.

Additional context

In previous PRs we solved this issue for notebooks:

• Fix cell modifications causing cell output reload and shift to active cell index #360
• Improve reloading of documents to avoid spurious side-effects #355

We could use difflib.SequenceMatcher to solve this for text files.