fix: enable Globe+F (fn+F) fullscreen shortcut

[datlechin]

Summary

• SwiftUI lifecycle apps don't create a real NSMenuItem for "Enter Full Screen" — the fn F shortcut shown in the View menu is a visual hint only, with no key equivalent binding
• macOS maps Globe+F (fn+F) to ⌃⌘F at the system level, but without a real menu item, the keystroke has no target
• Install a local event monitor in AppDelegate that catches ⌃⌘F and calls toggleFullScreen(nil) on the key window

Investigation

• Debug dump of View menu confirmed "Enter Full Screen" does not exist as a real NSMenuItem
• Verified no existing code (VimKeyInterceptor, EditorEventRouter, InlineSuggestionManager) intercepts ⌃⌘F
• Tested removing Toggle Filters (Cmd+F) shortcut — fn+F still didn't work, ruling out subset modifier matching
• Tested explicitly setting .fullScreenPrimary on main windows — didn't trigger macOS to create a real menu item

Test plan

• Press fn+F (Globe+F) → enters fullscreen
• Press fn+F again → exits fullscreen
• Verify Cmd+F still toggles filters
• Verify Option+click green button still works
• Verify View menu → "Enter Full Screen" click still works