tools: WSL ticker for timing-verification takes

Absolute-deadline 1s marker (CLOCK_REALTIME clock_nanosleep, user-readable
timestamp + drift per second) so a recording's real-time pace is checkable
on screen. Deadline pacing mirrors game-loop/OBS canon -
stackoverflow.com/questions/5441464. Build: gcc -O2 -o ticker ticker.c

tools/ticker.c

@@ -0,0 +1,37 @@
+#include <errno.h>
+#include <inttypes.h>
+#include <signal.h>
+#include <stdio.h>
+#include <time.h>
+
+static volatile sig_atomic_t g_run = 1;
+static void stop(int s){ (void)s; g_run = 0; }
+
+static double mono(void){
+    struct timespec t; clock_gettime(CLOCK_MONOTONIC, &t);
+    return (double)t.tv_sec + (double)t.tv_nsec/1e9;
+}
+
+int main(void){
+    signal(SIGINT, stop); signal(SIGTERM, stop);
+    struct timespec base; clock_gettime(CLOCK_REALTIME, &base);
+    base.tv_nsec = 0; base.tv_sec += 1;
+    double t0 = mono();
+    uint64_t tick = 0;
+
+    while (g_run){
+        struct timespec dl = base;
+        dl.tv_sec += (time_t)tick;
+        int rc = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &dl, NULL);
+        if (rc != 0 && rc != EINTR) break;
+        double now = mono();
+        double drift = (now - t0 - (double)tick) * 1e3;
+        struct timespec r; clock_gettime(CLOCK_REALTIME, &r);
+        struct tm mv; localtime_r(&r.tv_sec, &mv);
+        printf("[%05" PRIu64 "] t+%09.6fs drift %+7.2fms %02d:%02d:%02d\n",
+               tick, now - t0, drift, mv.tm_hour, mv.tm_min, mv.tm_sec);
+        fflush(stdout);
+        tick++;
+    }
+    return 0;
+}