Not doing spell check in schoology

**Describe the bug**
Harper dosent work on powerschool / schoology
**To Reproduce**
Steps to reproduce the behavior:
1. Go to powerschool schoology
2. Try to type in a box
4. See error

**Expected behavior**
Harper should work in these text boxes.

**Additional context**
According to an LLM the text box is this "TinyMCE-based Rich Text Editor (RTE) loaded inside an `` framework

Thanks I really injoy using Harper its way better than Grammarly.

No repository files or tests are named. Start by reproducing the failure in the PowerSchool and Schoology text boxes, then investigate how Harper reaches TinyMCE-based rich-text editors inside iframes. Done means spell checking works in those text boxes and the behavior is covered by an appropriate regression check.

Written by the indexing model from the issue text.