macOS: save/restore firstResponder on non-native fullscreen (#7279)

Fixes #6999
Supersedes #7201 

It appears that at some point one of the operations causes focus to move
away for non-native fullscreen. We previously relied on the delegate
method to restore this but a better approach appears to handle this
directly in the fullscreen implementations. This fixes the linked issue.

I still think long term all the `Ghostty.moveFocus` stuff is a code
smell and we should be auditing all that code to see if we can eliminate
it. But this is a step in the right direction, and removes one of those
uses.

macos/Sources/Features/Terminal/BaseTerminalController.swift

@@ -361,14 +361,6 @@ class BaseTerminalController: NSWindowController,
         }
     }
 
-    func fullscreenDidChange() {
-        // For some reason focus can get lost when we change fullscreen. Regardless of
-        // mode above we just move it back.
-        if let focusedSurface {
-            Ghostty.moveFocus(to: focusedSurface)
-        }
-    }
-
     // MARK: Clipboard Confirmation
 
     @objc private func onConfirmClipboardRequest(notification: SwiftUI.Notification) {

macos/Sources/Features/Terminal/TerminalController.swift

@@ -121,9 +121,7 @@ class TerminalController: BaseTerminalController {
     }
 
 
-    override func fullscreenDidChange() {
-        super.fullscreenDidChange()
-
+    func fullscreenDidChange() {
         // When our fullscreen state changes, we resync our appearance because some
         // properties change when fullscreen or not.
         guard let focusedSurface else { return }

macos/Sources/Helpers/Fullscreen.swift

@@ -171,6 +171,13 @@ class NonNativeFullscreen: FullscreenBase, FullscreenStyle {
         guard let savedState = SavedState(window) else { return }
         self.savedState = savedState
 
+        // Get our current first responder on this window. For non-native fullscreen
+        // we have to restore this because for some reason the operations below
+        // lose it (see: https://github.com/ghostty-org/ghostty/issues/6999).
+        // I don't know the root cause here so if we can figure that out there may
+        // be a nicer way than this.
+        let firstResponder = window.firstResponder
+
         // We hide the dock if the window is on a screen with the dock.
         // We must hide the dock FIRST then hide the menu:
         // If you specify autoHideMenuBar, it must be accompanied by either hideDock or autoHideDock.
@@ -207,6 +214,10 @@ class NonNativeFullscreen: FullscreenBase, FullscreenStyle {
         // https://github.com/ghostty-org/ghostty/issues/1996
         DispatchQueue.main.async {
             self.window.setFrame(self.fullscreenFrame(screen), display: true)
+            if let firstResponder {
+                self.window.makeFirstResponder(firstResponder)
+            }
+
             self.delegate?.fullscreenDidChange()
         }
     }
@@ -220,6 +231,9 @@ class NonNativeFullscreen: FullscreenBase, FullscreenStyle {
         let center = NotificationCenter.default
         center.removeObserver(self, name: NSWindow.didChangeScreenNotification, object: window)
 
+        // See enter where we do the same thing to understand why.
+        let firstResponder = window.firstResponder
+
         // Unhide our elements
         if savedState.dock {
             unhideDock()
@@ -258,6 +272,10 @@ class NonNativeFullscreen: FullscreenBase, FullscreenStyle {
             }
         }
 
+        if let firstResponder {
+            window.makeFirstResponder(firstResponder)
+        }
+
         // Unset our saved state, we're restored!
         self.savedState = nil