agent_ui: Fix inconsistent Rules keybinding in Toggle Agent Menu

[galuis116]

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Closes #54419

Release Notes:

• Fixed Agent menu shortcut context handling so Alt-Shift-L consistently resolves to Rules (and displays correctly) when the Toggle Agent Menu is open, while preserving existing global/context-specific shortcuts such as Language Servers and onboarding bindings outside Agent menu context.

[galuis116]

Hello @maxdeviant, I am waiting to check this pull request and merge.

[danilo-leal]

Thanks! I pushed a fix simplifying it; having the menu take the focus is already enough to make the Rules keybinding not get overridden by whatever else uses the same binding.