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/time_precise.h

@@ -0,0 +1,41 @@
+#ifndef _WDL_TIME_PRECISE_H_
+#define _WDL_TIME_PRECISE_H_
+
+#ifdef _WIN32
+#include <windows.h>
+#elif defined(__APPLE__)
+#include <sys/time.h>
+#else
+#include <time.h>
+#endif
+
+#include "wdltypes.h"
+
+
+#ifdef WDL_TIME_PRECISE_DECL
+WDL_TIME_PRECISE_DECL
+#else
+static WDL_STATICFUNC_UNUSED
+#endif
+
+double time_precise()
+{
+#ifdef _WIN32
+  LARGE_INTEGER freq;
+  QueryPerformanceFrequency(&freq);
+
+  LARGE_INTEGER now;
+  QueryPerformanceCounter(&now);
+  return (double)now.QuadPart / (double)freq.QuadPart;
+#elif defined(__APPLE__)
+  struct timeval tm={0,};
+  gettimeofday(&tm,NULL);
+  return (double)tm.tv_sec + (double)tm.tv_usec/1000000;
+#else
+  struct timespec tm={0,};
+  clock_gettime(CLOCK_MONOTONIC,&tm);
+  return (double)tm.tv_sec + (double)tm.tv_nsec/1000000000;
+#endif
+}
+
+#endif