fix: bundle full Helper .app inside .vst3 and spawn it correctly

The bare executable doesn't work — JUCE needs the .app bundle structure
(Info.plist etc.) to initialize the message loop and plugin formats.

Fix: copy entire PluginBridgeHelper.app into .vst3/Contents/Resources/
and spawn via the MacOS/PluginBridgeHelper path inside it.

CMakeLists.txt

@@ -112,7 +112,8 @@ target_link_libraries(PluginBridgeHelper
 )
 
 # ─────────────────────────────────────────────────────────────
-# Post-build: Copy PluginBridgeHelper into the .vst3 bundle
+# Post-build: Copy full PluginBridgeHelper.app into the .vst3 bundle
+# The .app structure is required for JUCE to initialize properly.
 # ─────────────────────────────────────────────────────────────
 
 add_dependencies(PluginBridge PluginBridgeHelper)
@@ -120,8 +121,10 @@ add_dependencies(PluginBridge PluginBridgeHelper)
 add_custom_command(TARGET PluginBridge POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E make_directory
         "$<TARGET_BUNDLE_DIR:PluginBridge_VST3>/Contents/Resources"
-    COMMAND ${CMAKE_COMMAND} -E copy
-        "$<TARGET_FILE:PluginBridgeHelper>"
-        "$<TARGET_BUNDLE_DIR:PluginBridge_VST3>/Contents/Resources/PluginBridgeHelper"
-    COMMENT "Bundling PluginBridgeHelper inside PluginBridge.vst3"
+    COMMAND ${CMAKE_COMMAND} -E rm -rf
+        "$<TARGET_BUNDLE_DIR:PluginBridge_VST3>/Contents/Resources/PluginBridgeHelper.app"
+    COMMAND ${CMAKE_COMMAND} -E copy_directory
+        "$<TARGET_BUNDLE_DIR:PluginBridgeHelper>"
+        "$<TARGET_BUNDLE_DIR:PluginBridge_VST3>/Contents/Resources/PluginBridgeHelper.app"
+    COMMENT "Bundling PluginBridgeHelper.app inside PluginBridge.vst3"
 )