Add delay before a title change to avoid flicker on macOS (#2929)

Implements #2503 for macOS

This PR introduces a delay (75ms) before a title change to avoid the
flicker caused by fast running commands.

It adds a timer to `titleDidChange` in the
[BaseTerminalController](https://github.com/ghostty-org/ghostty/blob/main/macos/Sources/Features/Terminal/BaseTerminalController.swift)
to delay the window title update.

However, this alone didn't work with `macos-titlebar-style = tabs` as
the main window title is hidden and toolbar tab titles are set
separately in
[TerminalController](https://github.com/ghostty-org/ghostty/blob/main/macos/Sources/Features/Terminal/TerminalController.swift).
I have added another timer in there to avoid flicker for tab titles.

I also tried @qwerasd205's suggested approach by putting the timer in
the
[SurfaceView](https://github.com/ghostty-org/ghostty/blob/main/macos/Sources/Ghostty/SurfaceView_AppKit.swift)
and setting it inside `setTitle` in
[Ghostty.App](https://github.com/ghostty-org/ghostty/blob/main/macos/Sources/Ghostty/Ghostty.App.swift),
and that also works. Maybe this a better approach as it avoids having
two timers?

There is still a flicker from the title changing from default "👻
Ghostty" to the current directory when opening new tabs but neither
approach fixes that. Not too sure how to prevent that.

Before:


https://github.com/user-attachments/assets/bd87ff36-9888-4d01-904a-2e80b8edea18

After:


https://github.com/user-attachments/assets/dae8eb24-8ae0-4412-ab84-bf313aac8063

macos/Sources/Ghostty/Ghostty.App.swift

@@ -947,14 +947,7 @@ extension Ghostty {
                 guard let surface = target.target.surface else { return }
                 guard let surfaceView = self.surfaceView(from: surface) else { return }
                 guard let title = String(cString: v.title!, encoding: .utf8) else { return }
-
-                // We must set this in a dispatchqueue to avoid a deadlock on startup on some
-                // versions of macOS. I unfortunately didn't document the exact versions so
-                // I don't know when its safe to remove this.
-                DispatchQueue.main.async {
-                    surfaceView.title = title
-                }
-
+                surfaceView.setTitle(title)
 
             default:
                 assertionFailure()
@@ -1089,7 +1082,10 @@ extension Ghostty {
                 guard let surface = target.target.surface else { return }
                 guard let surfaceView = self.surfaceView(from: surface) else { return }
                 let backingSize = NSSize(width: Double(v.width), height: Double(v.height))
+                DispatchQueue.main.async { [weak surfaceView] in
+                    guard let surfaceView else { return }
                     surfaceView.cellSize = surfaceView.convertFromBacking(backingSize)
+                }
 
             default:
                 assertionFailure()

macos/Sources/Ghostty/SurfaceView_AppKit.swift

@@ -12,7 +12,7 @@ extension Ghostty {
         // The current title of the surface as defined by the pty. This can be
         // changed with escape codes. This is public because the callbacks go
         // to the app level and it is set from there.
-        @Published var title: String = "👻"
+        @Published private(set) var title: String = "👻"
 
         // The current pwd of the surface as defined by the pty. This can be
         // changed with escape codes.
@@ -110,6 +110,9 @@ extension Ghostty {
         // This is set to non-null during keyDown to accumulate insertText contents
         private var keyTextAccumulator: [String]? = nil
 
+        // A small delay that is introduced before a title change to avoid flickers
+        private var titleChangeTimer: Timer?
+
         // We need to support being a first responder so that we can get input events
         override var acceptsFirstResponder: Bool { return true }
 
@@ -339,6 +342,20 @@ extension Ghostty {
             NSCursor.setHiddenUntilMouseMoves(!visible)
         }
 
+        func setTitle(_ title: String) {
+            // This fixes an issue where very quick changes to the title could
+            // cause an unpleasant flickering. We set a timer so that we can
+            // coalesce rapid changes. The timer is short enough that it still
+            // feels "instant".
+            titleChangeTimer?.invalidate()
+            titleChangeTimer = Timer.scheduledTimer(
+                withTimeInterval: 0.075,
+                repeats: false
+            ) { [weak self] _ in
+                self?.title = title
+            }
+        }
+
         // MARK: - Notifications
 
         @objc private func onUpdateRendererHealth(notification: SwiftUI.Notification) {