fix(build): drop macosx from SUPPORTED_PLATFORMS (iOS-only app)

The dual-backend merge (2e49820) widened SUPPORTED_PLATFORMS to
"iphoneos iphonesimulator macosx" across all targets -- almost certainly an
Xcode side effect of adding the sibling SPM packages (reticulum/LXMF/LXST-swift),
which all declare .macOS(.v13). But the embedded Python.xcframework ships only
iOS slices (ios-arm64, ios-arm64_x86_64-simulator), so any macOS evaluation
fails with 'no library for this platform was found in Python.xcframework'.

All three targets are iOS products (app, app-extension, unit-test) with
SDKROOT=iphoneos -- none is a real macOS target -- so macosx is spurious.
Restrict to "iphoneos iphonesimulator".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: torlando-agent[bot]

Columba.xcodeproj/project.pbxproj

@@ -1199,7 +1199,7 @@
 				MARKETING_VERSION = 0.0.2;
 				PRODUCT_BUNDLE_IDENTIFIER = network.columba.Columba;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = "$(inherited) COLUMBA_BACKEND_SWIFT";
 				SWIFT_EMIT_LOC_STRINGS = YES;
@@ -1245,7 +1245,7 @@
 				ONLY_ACTIVE_ARCH = YES;
 				PRODUCT_BUNDLE_IDENTIFIER = network.columba.Columba;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = "$(inherited) COLUMBA_BACKEND_SWIFT";
 				SWIFT_EMIT_LOC_STRINGS = YES;
@@ -1266,7 +1266,7 @@
 				MACOSX_DEPLOYMENT_TARGET = 14.0;
 				PRODUCT_BUNDLE_IDENTIFIER = network.columba.Columba.tests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_ENABLE_EXPLICIT_MODULES = NO;
@@ -1371,7 +1371,7 @@
 				MACOSX_DEPLOYMENT_TARGET = 14.0;
 				PRODUCT_BUNDLE_IDENTIFIER = network.columba.Columba.tests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_ENABLE_EXPLICIT_MODULES = NO;
@@ -1617,7 +1617,7 @@
 				ONLY_ACTIVE_ARCH = YES;
 				PRODUCT_BUNDLE_IDENTIFIER = network.columba.Columba;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_EMIT_LOC_STRINGS = YES;
 				SWIFT_OBJC_BRIDGING_HEADER = "Sources/PythonBridge/ColumbaPython-Bridging-Header.h";
@@ -1661,7 +1661,7 @@
 				MARKETING_VERSION = 0.0.2;
 				PRODUCT_BUNDLE_IDENTIFIER = network.columba.Columba;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_EMIT_LOC_STRINGS = YES;
 				SWIFT_OBJC_BRIDGING_HEADER = "Sources/PythonBridge/ColumbaPython-Bridging-Header.h";
@@ -1681,7 +1681,7 @@
 				MACOSX_DEPLOYMENT_TARGET = 14.0;
 				PRODUCT_BUNDLE_IDENTIFIER = network.columba.Columba.tests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_ENABLE_EXPLICIT_MODULES = NO;
@@ -1702,7 +1702,7 @@
 				MACOSX_DEPLOYMENT_TARGET = 14.0;
 				PRODUCT_BUNDLE_IDENTIFIER = network.columba.Columba.tests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_ENABLE_EXPLICIT_MODULES = NO;