[RTE] Long formula overflows container in editor, viewer, and tree view preview #5935

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Observed behavior

When a formula node inside the Rich Text Editor (RTE) contains a long expression, the formula overflows the boundaries of its container in editor mode, viewer mode, and the content node preview in the tree view — the formula renders beyond the right edge without wrapping or clipping.

Expected behavior

The formula should not overflow its container. The correct behavior is TBD — options include showing a scrollbar on the formula node itself, or showing a scrollbar on the RTE container — but in either case the formula should not render outside its boundaries.

User-facing consequences

Content creators see broken layouts when a question contains a long formula — the formula overflows its container in the assessment editor (both edit and view modes) and in the content node preview in the tree view, making the UI look visually incorrect.

Steps to reproduce

1. Create a new exercise node in Studio.
2. Add a question.
3. In the question field, insert a formula with a long expression (e.g., This > is > a > very > very > very > very > very > very > long > formula).
4. Observe that the formula overflows the right boundary of the RTE container in edit mode.
5. Close the editor and observe the same overflow in viewer mode and in the content node preview in the tree view.

AI usage

Used Claude to help draft this issue from a description and screenshots. Reviewed and confirmed all sections for accuracy.