feat(macos): migrate menu to SwiftUI App + .commands

Replace the programmatic AppKit menu bar (added in #2836) with the SwiftUI
App lifecycle. SwiftUI provides the standard App/File/Edit/View/Window/Help
menus for free, so the ~320 lines of makeMainMenu/make*MenuItem in
WindowController.swift are deleted.

The dynamic "React" menu is now declarative: ReactCommands renders a
CommandMenu("React") driven by an observable AppModel. Publishing
components/componentsEnabled/rememberLastComponent rebuilds the menu, so the
manual NSMenuItem add/remove bookkeeping is gone. An AppDelegate is kept via
@NSApplicationDelegateAdaptor for RN setup and lifecycle notifications.

- AppDelegate.swift: @main App struct + adaptor + AppModel
- ReactCommands.swift: dynamic React menu (Cmd-Shift-1..9 component shortcuts)
- ViewController.swift: SwiftUI content hosting + placeholder
- WindowController.swift: deleted
- project.pbxproj / pack.test.mts: swap WindowController.swift for ReactCommands.swift

Both ENABLE_SINGLE_APP_MODE and multi-app behavior are preserved.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Saadnajmi

packages/app/macos/ReactTestApp.xcodeproj/project.pbxproj

@@ -16,7 +16,7 @@
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 		196C22652490CBAB00449D3C /* React+Compatibility.m in Sources */ = {isa = PBXBuildFile; fileRef = 196C22632490CBAB00449D3C /* React+Compatibility.m */; };
-		199F3E152FF7AA0000270357 /* WindowController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 199F3E142FF7A9FB00270357 /* WindowController.swift */; };
+		1900C0DE2FF9AA0000000002 /* ReactCommands.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1900C0DE2FF9AA0000000001 /* ReactCommands.swift */; };
 		19C4C89327710D8500157870 /* Manifest+Embedded.g.swift in Sources */ = {isa = PBXBuildFile; fileRef = 19C4C89227710D8500157870 /* Manifest+Embedded.g.swift */; };
 		19E791C024B08E1400FA6468 /* ReactTestAppTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 19E791BF24B08E1400FA6468 /* ReactTestAppTests.swift */; };
 		19E791C324B08E4D00FA6468 /* ReactTestAppUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 19E791C224B08E4D00FA6468 /* ReactTestAppUITests.swift */; };
@@ -59,7 +59,7 @@
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 		196C22632490CBAB00449D3C /* React+Compatibility.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = "React+Compatibility.m"; path = "../Shared/React+Compatibility.m"; sourceTree = "<group>"; };
 		196C22642490CBAB00449D3C /* React+Compatibility.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = "React+Compatibility.h"; path = "../Shared/React+Compatibility.h"; sourceTree = "<group>"; };
-		199F3E142FF7A9FB00270357 /* WindowController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WindowController.swift; sourceTree = "<group>"; };
+		1900C0DE2FF9AA0000000001 /* ReactCommands.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ReactCommands.swift; sourceTree = "<group>"; };
 		19B368BC24B12C24002CCEFF /* ReactTestApp.common.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = ReactTestApp.common.xcconfig; sourceTree = "<group>"; };
 		19B368BD24B12C24002CCEFF /* ReactTestApp.debug.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = ReactTestApp.debug.xcconfig; sourceTree = "<group>"; };
 		19B368BE24B12C24002CCEFF /* ReactTestApp.release.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = ReactTestApp.release.xcconfig; sourceTree = "<group>"; };
@@ -117,12 +117,12 @@
 			isa = PBXGroup;
 			children = (
 				193EF062247A736200BE8C79 /* AppDelegate.swift */,
+				1900C0DE2FF9AA0000000001 /* ReactCommands.swift */,
 				193EF08E247A799D00BE8C79 /* Manifest.swift */,
 				19C4C89227710D8500157870 /* Manifest+Embedded.g.swift */,
 				193EF097247B130700BE8C79 /* ReactInstance.swift */,
 				1960F338258C97C400AEC7A2 /* Session.swift */,
 				193EF064247A736200BE8C79 /* ViewController.swift */,
-				199F3E142FF7A9FB00270357 /* WindowController.swift */,
 				193EF094247A84DA00BE8C79 /* ReactTestApp-Bridging-Header.h */,
 				196C22642490CBAB00449D3C /* React+Compatibility.h */,
 				196C22632490CBAB00449D3C /* React+Compatibility.m */,
@@ -315,10 +315,10 @@
 			buildActionMask = 2147483647;
 			files = (
 				193EF063247A736200BE8C79 /* AppDelegate.swift in Sources */,
+				1900C0DE2FF9AA0000000002 /* ReactCommands.swift in Sources */,
 				193EF08F247A799D00BE8C79 /* Manifest.swift in Sources */,
 				19C4C89327710D8500157870 /* Manifest+Embedded.g.swift in Sources */,
 				196C22652490CBAB00449D3C /* React+Compatibility.m in Sources */,
-				199F3E152FF7AA0000270357 /* WindowController.swift in Sources */,
 				193EF098247B130700BE8C79 /* ReactInstance.swift in Sources */,
 				1960F339258C97C400AEC7A2 /* Session.swift in Sources */,
 				193EF093247A830200BE8C79 /* UIViewController+ReactTestApp.m in Sources */,