Hover-activated activity rail interferes with normal sidebar navigation

Description

The vertical activity / preview rail between the sidebar and the main conversation area is currently too easy to trigger accidentally.

When working with multiple projects, I frequently move the mouse from the main conversation area toward the left sidebar to select another project. That movement path crosses directly over this rail. As soon as the cursor touches it, a preview popover opens unexpectedly.

This makes ordinary project switching feel fragile and frustrating. The app should assume that users often move between the main thread and the project list, especially when managing many projects.

Steps to reproduce

1. Open Codex with the sidebar visible.
2. Have multiple projects listed in the sidebar.
3. Move the mouse from the main conversation area toward the project list.
4. Pass over the vertical dashed/striped activity rail.
5. A preview popover opens even though the user was only trying to reach the sidebar.

Expected behavior

Moving the mouse toward the sidebar should not open unrelated previews or panels. Project switching should remain predictable and calm.

Actual behavior

The hover rail opens a preview popover unintentionally and interrupts the user's path to the project list.

Why this matters

This is especially disruptive for users who work with many projects. Selecting projects from the sidebar is a core workflow. A hover target placed directly in that movement path creates constant accidental activations.

Suggested improvements

Please consider one or more of the following:

• Add a setting to disable this hover rail entirely.
• Require an explicit click instead of hover activation.
• Add a meaningful hover delay before opening previews.
• Move the trigger away from the normal path between the thread and the sidebar.
• Reduce the width/sensitivity of the hover target.
• Allow users to collapse or hide the activity/preview rail.

Screenshot

Redacted screenshot attached below. It masks private project and thread content while preserving the hover rail and preview popover.

<img width="1400" height="910" alt="Image" src="https://github.com/user-attachments/assets/0924e037-dc9a-4ce6-bde3-f56346abe8d6" />