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/timing.h

@@ -0,0 +1,42 @@
+/*
+  WDL - timing.h
+
+  this is based on some public domain Pentium RDTSC timing code from usenet in 1996.
+
+  To enable this, your app must #define TIMING, include timing.h, and call timingEnter(x)/timingLeave(x) a bunch
+  of times (where x is 0..63).
+
+*/
+
+#ifndef _TIMING_H_
+#define _TIMING_H_
+
+
+//#define TIMING
+
+
+#include "wdltypes.h"
+
+#if defined(TIMING)
+#ifdef __cplusplus
+extern "C" {
+#endif
+void _timingEnter(int);
+void _timingLeave(int);
+WDL_INT64 _timingQuery(int, WDL_INT64*);
+#ifdef __cplusplus
+}
+#endif
+#define timingLeave(x) _timingLeave(x)
+#define timingEnter(x) _timingEnter(x)
+#define timingQuery(x,y) _timingQuery(x,y)
+#else
+#define timingLeave(x)
+#define timingEnter(x)
+#define timingQuery(x,y) (0)
+#endif
+
+#define timingPrint()
+#define timingInit()
+
+#endif