T40: review round 1: a notification names the session as the output stands at its place: the tap follows OSC 0 and 2, the title stack's CSI 22 t and 23 t and a full reset as alacritty does, and sends each title in order, since alacritty's own title events come after the tap's; one write and split writes post the same

src/term/pty.rs

@@ -25,6 +25,8 @@ pub enum PtyEvent {
     Status(Status),
     /// A notification or progress, OSC 9, 777 or 99.
     Ask(Ask),
+    /// A title a program set, in the output's order: OSC 0 or 2, or the title stack's pop.
+    Title(String),
     /// A full reset, `ESC c`.
     Reset,
 }