feat: eliminate Editor.xib with programmatic NSWindow + SwiftUI root

Source/ApplicationController.h

@@ -26,10 +26,8 @@
 
 @interface ApplicationController : NSObject {
 	@private
-	IBOutlet NSProgressIndicator *busyIndicator;
 	IBOutlet HostsMainController *hostsController;
 	IBOutlet NSMenuItem *checkForUpdatesMenuItem;
-	int busyThreads;
 	BOOL shouldQuit;
 	BOOL editorWindowOpened;
 	SPUStandardUpdaterController *_updaterController;

Source/ApplicationController.m

@@ -31,7 +31,6 @@
 @interface ApplicationController ()
 {
 	__weak NSWindow *_editorWindow;
-	NSArray *_editorNibTopLevelObjects; // retains top-level NIB objects (e.g. EditorController)
 }
 @end
 
@@ -62,7 +61,6 @@ - (id)init
         return sharedInstance;
     }
 	if (self = [super init]) {
-		busyThreads = 0;
 		shouldQuit = YES;
 
 		BOOL isTesting = NSClassFromString(@"XCTestCase") != nil;
@@ -118,7 +116,7 @@ -(IBAction)quit:(id)sender
 - (IBAction)openEditorWindow:(id)sender
 {
 	if (!editorWindowOpened) {
-		if (_editorNibTopLevelObjects) {
+		if (_editorWindow) {
 			editorWindowOpened = YES;
 			[[NSNotificationCenter defaultCenter] addObserver:self
 													 selector:@selector(editorWindowWillClose:)
@@ -167,22 +165,6 @@ - (BOOL)editorWindowOpened
 	return editorWindowOpened;
 }
 
-- (void)increaseBusyThreadsCount:(NSNotification *)notification
-{
-	busyThreads++;
-	[busyIndicator startAnimation:self];
-}
-
-- (void)decreaseBusyThreadsCount:(NSNotification *)notification
-{
-	if (busyThreads > 0) {
-		busyThreads--;
-	}
-	if (busyThreads == 0) {
-		[busyIndicator stopAnimation:self];
-	}
-}
-
 #pragma mark - Application Delegate
 
 - (void)applicationWillFinishLaunching:(NSNotification *)aNotification
@@ -195,11 +177,7 @@ - (void)applicationWillFinishLaunching:(NSNotification *)aNotification
 	[NSApp setServicesProvider:self];
 
 	[self initStructure];
-
-	NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
-	[nc addObserver:self selector:@selector(increaseBusyThreadsCount:) name:ThreadBusyNotification object:nil];
-	[nc addObserver:self selector:@selector(decreaseBusyThreadsCount:) name:ThreadNotBusyNotification object:nil];
-
+
 	[hostsController load];
 
 	if (!openedAtLogin() && [Preferences showEditorWindow]) {
@@ -286,20 +264,12 @@ - (void)initStructure
 - (void)initEditorWindow
 {
 	logDebug(@"Initializing editor window");
-	NSArray *topLevelObjects = nil;
-	[[NSBundle mainBundle] loadNibNamed:@"Editor" owner:self topLevelObjects:&topLevelObjects];
-	_editorNibTopLevelObjects = topLevelObjects;
+	_editorWindow = [EditorWindowPresenter createEditorWindow];
 	editorWindowOpened = YES;
-	for (id obj in topLevelObjects) {
-		if ([obj isKindOfClass:[NSWindow class]]) {
-			_editorWindow = obj;
-			[[NSNotificationCenter defaultCenter] addObserver:self
-													 selector:@selector(editorWindowWillClose:)
-														 name:NSWindowWillCloseNotification
-													   object:obj];
-			break;
-		}
-	}
+	[[NSNotificationCenter defaultCenter] addObserver:self
+											 selector:@selector(editorWindowWillClose:)
+												 name:NSWindowWillCloseNotification
+											   object:_editorWindow];
 }
 
 - (void)activatePreviousFile:(NSNotification *)note