MDN "In this article" sidebar becomes squeezed when Gemini side panel is opened

Hi! I noticed a layout issue while reading the MDN JavaScript documentation.

When I open Chrome's Gemini side panel on the right, the "In this article" navigation on the left side of the MDN page becomes very narrow, causing the text to wrap awkwardly.

When I close the Gemini side panel, the MDN layout immediately returns to normal.

Steps to reproduce

1. Open this MDN page:
   https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/Scripting/What_is_JavaScript#how_do_you_add_javascript_to_your_page
2. Make sure the page is displayed normally.
3. Open the Gemini side panel on the right side of Chrome.
4. Look at the "In this article" navigation on the left.
5. Close the Gemini side panel.

Expected behavior

The "In this article" navigation should remain properly sized and readable when the available browser width changes.

Actual behavior

Opening the Gemini side panel causes the left "In this article" navigation to become very narrow, making the text wrap awkwardly.

Closing the Gemini panel immediately restores the normal layout.

I was able to reproduce this behavior multiple times using the same steps.

Environment

• Browser: Google Chrome 152.0.7977.83
• OS: Windows 11 25H2
• Gemini: Chrome side panel

I'm not sure whether this is caused by MDN's responsive layout, Chrome's side-panel behavior, or an interaction between the two, but I thought it was worth reporting because the behavior is reproducible.

I've attached screenshots showing the normal and affected states.

Start by reproducing the issue on the linked MDN JavaScript page, comparing the “In this article” navigation before and after opening Chrome’s Gemini side panel. Trace the frontend layout behavior at the reduced available width; done means the navigation remains properly sized and readable while the panel is open and returns to normal when it closes.