documents: an open block stays open while an overlay borrows focus

A menu or dialog took focus, the open block wrote back and closed, and
the overlay handed focus back to a closed input: its command reached
nothing and the selection was gone. The block now waits for the overlay
to let focus go, and writes back only when focus lands elsewhere.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/primitives/mod.rs

@@ -25,7 +25,8 @@ pub use divider::Divider;
 pub use files::IconTheme;
 pub(crate) use files::{file_icon, icon_theme};
 pub(crate) use focus::{
-    CONTEXT as FOCUS_CONTEXT, Takeover, give_back, hand_back, hold_focus, tab_stop, take_focus,
+    CONTEXT as FOCUS_CONTEXT, Takeover, give_back, hand_back, hold_focus, lent, tab_stop,
+    take_focus,
 };
 pub use focus::{FocusNext, FocusPrev, FocusRing, FocusScope};
 pub use ghost::DragGhost;