Feedback button deletes essay content

# Feedback button deletes essay content

Clicking "Get feedback" on a document deletes parts of the essay. Once it happens to a student, it keeps happening on that document until they create a new one.

## Reproduction

1. As a student, write in a document.
2. Click "Get feedback".
3. Observe parts of the essay text disappearing from the editor.

Hard to reproduce on demand — appears non-deterministic across students, but deterministic per-document once it starts.

## Expected

Get feedback runs without modifying the editor's content. Edits are non-destructive.

## Actual

Recent edits in the document get deleted when feedback is requested. The deletions are not full reverts — partial content is removed.

## Impact

Data loss on student work. Reported on Apr 7 (11 students in one morning) and again Apr 8 (still hitting it after some changes were deployed). Students hitting this are blocked on the core feedback flow until they start over in a new document.

## Affected versions

First reported 2026-04-07. Apr 8 follow-up: "Looks like a few guys are still hitting feedback and some recent changes are deleting" — earlier fix attempt didn't fully land.

## Suspected cause

Editor state vs. feedback request state are racing. Likely the feedback API call is round-tripping a stale snapshot of the document and writing it back, clobbering local edits made after the snapshot was taken. Investigate the document save/sync path around the feedback request.

## Workaround

Create a new document and paste the content over. Workaround is itself painful and risks losing work.