Add shortcut for focus mode

[seatayu]

Pre-submission Checklist

• I have searched existing issues and confirmed this has not already been requested
• This is a feature request, not a bug report or support question

Area

Memo editor

Problem or Use Case

Focus Mode is great for distraction-free writing, but entering it currently requires
leaving the keyboard. For a tool whose core loop is "capture a thought as fast as possible," having to reach for the mouse every time I want to settle in and write a longer note breaks the flow.

Who Would Use This?

Anyone who writes multiple memos a day, especially longer, reflective entries where they deliberately want to enter Focus Mode.

Proposed Solution

Bind a keyboard shortcut to the existing toggleFocusMode editor action so Focus
Mode can be toggled without the mouse, with the same shortcut toggling it back off.
A natural default would be Cmd/Ctrl + Shift + F (F = Focus), but I'm happy with whatever keybinding the team prefers. Since the toggle logic already exists, this is mostly a keybinding registration rather than new functionality.

Alternatives Considered

There is no in-app alternative today — only the toolbar button.

Compatibility and Migration

Frontend-only UI enhancement. No changes to API, storage, permissions, or deployments, and no impact on existing users.

Examples

No response

Additional Context

No response