config: title can reload at runtime (#2906)

Related to #2898

src/Surface.zig

@@ -1182,6 +1182,14 @@ pub fn updateConfig(
         log.warn("failed to notify renderer of config change err={}", .{err});
     };
 
+    // If we have a title set then we update our window to have the
+    // newly configured title.
+    if (config.title) |title| try self.rt_app.performAction(
+        .{ .surface = self },
+        .set_title,
+        .{ .title = title },
+    );
+
     // Notify the window
     try self.rt_app.performAction(
         .{ .surface = self },

src/config/Config.zig

@@ -679,6 +679,12 @@ fullscreen: bool = false,
 /// The title Ghostty will use for the window. This will force the title of the
 /// window to be this title at all times and Ghostty will ignore any set title
 /// escape sequences programs (such as Neovim) may send.
+///
+/// This configuration can be reloaded at runtime. If it is set, the title
+/// will update for all windows. If it is unset, the next title change escape
+/// sequence will be honored but previous changes will not retroactively
+/// be set. This latter case may require you restart programs such as neovim
+/// to get the new title.
 title: ?[:0]const u8 = null,
 
 /// The setting that will change the application class value.