Fix palette outside-click listener cleanup (#5362)

[severe77]

Description

This PR fixes an issue where the palette outside-click listener was not always
cleaned up correctly when palettes were opened and closed repeatedly.

Previously, the listener was attached using a deferred setTimeout, which could
result in stale document.click listeners being added after the palette lifecycle
had already changed. Over time, this caused listener accumulation and memory growth
during long-running sessions.

The listener lifecycle is now fully deterministic and properly cleaned up.

Changes

• Removed deferred (setTimeout) attachment of the outside-click listener
• Ensured any existing outside-click listener is removed before adding a new one
• Cleaned up the listener immediately when the palette is closed
• Added a null-safe guard for menuContainer to prevent edge-case errors
• Kept the fix scoped strictly to js/palette.js

Notes

• Change is limited to outside-click listener lifecycle cleanup
• No functional behavior changes expected
• All Jest tests passed locally

Fixes #5362

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.