PR conversation page: User card popup clipped by diff view

[p134c0d3]

Bug Description

When viewing a PR conversation page, hovering over a commenter's name shows a user info card popup that gets partially hidden behind the PR diff view on the left side. Approximately half of the card is obscured by the diff container.

Steps to Reproduce

1. Open any pull request with comments
2. Hover over a commenter's avatar/name
3. Observe that the user info card popup is clipped by the diff view

Expected Behavior

The user info card should fully appear above/on top of all other page elements, including the diff view.

Actual Behavior

The card is partially hidden "behind" the PR diff container, making user information inaccessible.

Environment

• Browser: Helium (chromium-based)
• OS: macOS Tahoe 26
• Tested: Reproducible across multiple PRs

Likely Cause

This appears to be a CSS z-index/stacking context issue where the user card popup has a lower stacking order than the diff container.

Suggested Fix

Review and adjust z-index values or stacking context for the user card popover component to ensure it renders above the PR diff view.

[p134c0d3]

Attaching image of card being partially hidden by diff viewer for context.

[p134c0d3]

Suggested prompt to resolve this issue.

[AbhiVarde]

hey, checked this on Windows with both Chrome and Helium and the user card appears correctly on both. unable to reproduce on Windows. might be macOS-specific or related to the macOS Tahoe 26 environment.

if anyone else can reproduce on Mac that would help narrow it down.

happy to look into a fix if it gets confirmed.