fn+F / green-button fullscreen no longer enters native fullscreen (Ctrl+Cmd+F still works)

Environment
App: Claude desktop, version 1.46388.4
macOS: 26.6.2 (build 25G83)

Steps to reproduce

1. Open Claude desktop, Code tab.
2. Press fn+F (or click the green traffic-light button).

Expected
Window enters native macOS fullscreen (own Space).

Actual
Window stops at screen borders / maximizes in place, does not register as a fullscreen app (no new Space, no fullscreen menu bar behavior).

Workaround
Ctrl+Cmd+F correctly toggles native fullscreen.

Notes
Since the OS-level shortcut works, the window likely isn't declaring itself fullscreen-primary the normal way for fn+F / the button's own handler.