[lexical] Bug Fix: Resolve Firefox arrow key navigation issue in collapsible nodes (#8348)

[MohmedIkram]

Description

This PR fixes a Firefox-specific issue where arrow key navigation skips over collapsible content inside <details> elements.

Current Behavior

• In Firefox, pressing the down arrow from the collapsible title (<summary>) skips the content inside the collapsible.
• Similarly, arrow up from the next paragraph skips the entire collapsible block.
• This results in inconsistent navigation compared to Chrome and Safari.

Changes Made

• Implemented a fix to ensure arrow key navigation correctly moves between blocks inside collapsible nodes in Firefox.
• Added handling to prevent skipping of collapsible content during keyboard navigation.

Result

• Arrow key navigation now behaves consistently across browsers.
• Users can navigate into and out of collapsible content as expected.

Before

Screen.Recording.2026-04-12.at.1.41.54.PM.mov

After

Screen.Recording.2026-04-12.at.1.42.28.PM.mov

Closes #8348

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Project	Deployment	Actions	Updated (UTC)
lexical	Ready	Preview, Comment	Apr 14, 2026 4:44pm
lexical-playground	Ready	Preview, Comment	Apr 14, 2026 4:44pm

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[etrepum]

It's important to make sure that this behavior is tested. I don't see any changes to the relevant e2e tests, which will probably be in a failing state, but there should also be new test code to ensure the up and down arrows work as expected in all browsers with this node.