Fix macOS pixel format: use ARGB byte order in all raw ScanLine blending

On macOS Cocoa, TBitmap.pf32bit stores pixels in ARGB order
   (byte0=A, byte1=R, byte2=G, byte3=B) rather than BGRA used on
   Linux/Windows. All raw ScanLine pixel blending and channel mapping
   is now guarded with { DARWIN} to use the correct offsets.

   Also fix PortAudio library discovery on macOS: probe .dylib names
   (including Homebrew paths) before falling through to .so/.dll.

AudioOutput.pas

@@ -163,14 +163,22 @@ function PaOutCallback(inputBuffer, outputBuffer: Pointer;
 implementation
 
 const
-{$IFDEF UNIX}
+{$IFDEF DARWIN}
+  PA_LIBS: array[0..3] of AnsiString = (
+    'libportaudio.dylib',
+    'libportaudio.2.dylib',
+    '/usr/local/lib/libportaudio.dylib',
+    '/opt/homebrew/lib/libportaudio.dylib'
+  );
+{$ELSE}
+  {$IFDEF UNIX}
   PA_LIBS: array[0..3] of AnsiString = (
     'libportaudio.so.2',
     'libportaudio.so',
     'libportaudio.so.2.0.0',
     'libportaudio.so.0'
   );
-{$ELSE}
+  {$ELSE}
   PA_LIBS: array[0..5] of AnsiString = (
     'portaudio_x64.dll',
     'portaudio_x86.dll',
@@ -179,6 +187,7 @@ const
     'libportaudio.dll',
     'libportaudio64.dll'
   );
+  {$ENDIF}
 {$ENDIF}
   PA_NO_ERROR  = 0;
   PA_FLOAT32   = LongWord(1);
@@ -292,7 +301,11 @@ begin
 {$IFDEF WINDOWS}
     FLastError := 'PortAudio DLL not found. Put portaudio_x64.dll, portaudio.dll, or libportaudio-2.dll next to ewsdr.exe';
 {$ELSE}
+  {$IFDEF DARWIN}
+    FLastError := 'libportaudio not found. Install via: brew install portaudio';
+  {$ELSE}
     FLastError := 'libportaudio not found. sudo apt install libportaudio2';
+  {$ENDIF}
 {$ENDIF}
     Exit;
   end;