Implement the XTWINOPS (CSI t) control sequences that "make sense".

These sequences were implemented:

CSI 14 t - report the text area size in pixels
CSI 16 t - report the cell size in pixels
CSI 18 t - report the text area size in cells
CSI 21 t - report the window title

These sequences were not implemented because they manuipulate the window
state in ways that we do not want.

CSI 1 t
CSI 2 t
CSI 3 ; x ; y t
CSI 4 ; height ; width ; t
CSI 5 t
CSI 6 t
CSI 7 t
CSI 8 ; height ; width ; t
CSI 9 ; 0 t
CSI 9 ; 1 t
CSI 9 ; 2 t
CSI 9 ; 3 t
CSI 10 ; 0 t
CSI 10 ; 1 t
CSI 10 ; 2 t
CSI 24 t

These sequences were not implemented because they do not make sense in
a Wayland context:

CSI 11 t
CSI 13 t
CSI 14 ; 2 t

These sequences were not implemented because they provide information
about the screen that is unnecessary.

CSI 15 t
CSI 19 t

These sequences were not implemeted because Ghostty does not maintain an
icon title for windows.

CSI 20 t
CSI 22 ; 0 t
CSI 22 ; 1 t
CSI 23 ; 0 t
CSI 23 ; 1 t

These sequences were not implemented because of the additional
complexity of maintaining a stack of window titles.

CSI 22 ; 2 t
CSI 23 ; 2 t

src/apprt/surface.zig

@@ -18,6 +18,9 @@ pub const Message = union(enum) {
     /// of any length
     set_title: [256]u8,
 
+    /// Report the window title back to the terminal
+    report_title: ReportTitleStyle,
+
     /// Set the mouse shape.
     set_mouse_shape: terminal.MouseShape,
 
@@ -57,6 +60,10 @@ pub const Message = union(enum) {
 
     /// Report the color scheme
     report_color_scheme: void,
+
+    pub const ReportTitleStyle = enum {
+        csi_21_t,
+    };
 };
 
 /// A surface mailbox.