fix: resolve probe_ctx_t type tag, add DEFAULT_MAX_WAL_RECORDS macro, fix atomic type consistency, move ha_seed_jitter to ha.c, add API doc comments

src/controller/ha.c

@@ -2,18 +2,47 @@
 #include "ha.h"
 
 #include <errno.h>
+#include <fcntl.h>
 #include <pthread.h>
 #include <signal.h>
 #include <stdatomic.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
+#include <unistd.h>
 
 /* Circular-include safety: cluster_def.h includes ha.h (include-guarded),
  * and ha.h only forward-declares cluster_t — no cycle. */
 #include "xce/cluster_def.h"
 #include "persist.h"
 
+/* ── PRNG seeding ───────────────────────────────────────────── */
+
+void ha_seed_jitter(uint64_t *seed, int my_priority)
+{
+    uint8_t buf[8] = {0};
+    int fd = open("/dev/urandom", O_RDONLY);
+    if (fd >= 0) {
+        ssize_t n = 0;
+        while (n < 8) {
+            ssize_t r = read(fd, buf + n, (size_t)(8 - n));
+            if (r <= 0) break;
+            n += r;
+        }
+        close(fd);
+        if (n == 8) {
+            memcpy(seed, buf, 8);
+            if (*seed != 0) return;
+        }
+    }
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    *seed = (uint64_t)ts.tv_nsec
+          ^ ((uint64_t)my_priority << 56)
+          ^ ((uint64_t)getpid() << 16);
+}
+
 int ha_init(ha_state_t *ha, const ha_config_t *cfg, int my_priority)
 {
     if (!ha || !cfg)