Fix accidental macOS 27 deployment target bump

MACOSX_DEPLOYMENT_TARGET was silently bumped 26.2 -> 27.0 in commit
8451db1, most likely by Xcode beta auto-updating it when the project
was opened/built with the macOS 27 beta SDK. This shipped in the public
v2.4 release, meaning the app refused to launch on anything older than
macOS 27 beta. No code in the project actually requires macOS 27 APIs.

oAI.xcodeproj/project.pbxproj

@@ -282,7 +282,7 @@
 				IPHONEOS_DEPLOYMENT_TARGET = 27.0;
 				LD_RUNPATH_SEARCH_PATHS = "@executable_path/Frameworks";
 				"LD_RUNPATH_SEARCH_PATHS[sdk=macosx*]" = "@executable_path/../Frameworks";
-				MACOSX_DEPLOYMENT_TARGET = 27.0;
+				MACOSX_DEPLOYMENT_TARGET = 26.2;
 				MARKETING_VERSION = 2.4.0;
 				PRODUCT_BUNDLE_IDENTIFIER = com.oai.oAI;
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -326,7 +326,7 @@
 				IPHONEOS_DEPLOYMENT_TARGET = 27.0;
 				LD_RUNPATH_SEARCH_PATHS = "@executable_path/Frameworks";
 				"LD_RUNPATH_SEARCH_PATHS[sdk=macosx*]" = "@executable_path/../Frameworks";
-				MACOSX_DEPLOYMENT_TARGET = 27.0;
+				MACOSX_DEPLOYMENT_TARGET = 26.2;
 				MARKETING_VERSION = 2.4.0;
 				PRODUCT_BUNDLE_IDENTIFIER = com.oai.oAI;
 				PRODUCT_NAME = "$(TARGET_NAME)";