T10: focus in and out reach a program under mode 1004; the window wears the program's title; a bell is logged and silent; the scrollback setting caps history and trims it live; Cmd-F finds in the scrollback with Ely's FindWidget, matches washed, Enter older, Shift-Enter newer, new output searched again

src/term/mod.rs

@@ -1,4 +1,5 @@
 mod boxes;
+mod find;
 pub mod frame;
 pub mod ink;
 pub mod input;