Add bare-minimum extension-reaper-macos REAPER extension skeleton

C/C++ extension built directly against the vendored Cockos reaper-sdk
headers (no Rust/reaper-rs wrapper layer). Loads, registers a test
action, and confirms via REAPER's console — confirmed working in
REAPER 2026-07-15.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

extension-reaper-macos/vendor/reaper-sdk/WDL/lice/test/resource.h

@@ -0,0 +1,27 @@
+//{{NO_DEPENDENCIES}}
+// Microsoft Developer Studio generated include file.
+// Used by test.rc
+//
+#define IDD_DIALOG1                     101
+#define IDC_PNG1                        102
+#define IDI_MAIN                        103
+#define IDC_BUTTON1                     1000
+#define IDC_RECT                        1001
+#define IDC_BUTTON2                     1002
+#define IDC_COMBO1                      1002
+#define IDC_BUTTON3                     1003
+#define IDC_BUTTON4                     1004
+#define IDC_BUTTON5                     1005
+#define IDC_BUTTON6                     1006
+#define IDC_BUTTON7                     1007
+
+// Next default values for new objects
+// 
+#ifdef APSTUDIO_INVOKED
+#ifndef APSTUDIO_READONLY_SYMBOLS
+#define _APS_NEXT_RESOURCE_VALUE        104
+#define _APS_NEXT_COMMAND_VALUE         40001
+#define _APS_NEXT_CONTROL_VALUE         1003
+#define _APS_NEXT_SYMED_VALUE           101
+#endif
+#endif