feat(ha-heartbeat-liveness): verify ctrlhello integration and RDHUP cancel (task 3.2)

Verification task: confirmed config_repl.c handle_ctrlhello calls both
ha_on_heartbeat_received and ha_arm_heartbeat_timeout_vtask (delaymgr poll).
Confirmed ha_on_primary_ctrl_fd_rdhup leads with ha_disarm (Req 5.4).
No pthread_create in heartbeat arm path (Req 1.6). Add thread-count test.

.kiro/specs/ha-heartbeat-liveness/tasks.md

@@ -48,7 +48,7 @@
   - _Depends: 2.1_
   - _Boundary: cluster.c (opcode dispatch)_
 
-- [ ] 3.2 Verify config_repl.c ctrlhello integration and EPOLLRDHUP cancellation path
+- [x] 3.2 Verify config_repl.c ctrlhello integration and EPOLLRDHUP cancellation path
   - Confirm `ha_arm_heartbeat_timeout_vtask` call in `handle_ctrlhello` (config_repl.c:1380) still correctly arms the delaymgr poll (not a thread)
   - Confirm `ha_on_heartbeat_received` call at config_repl.c:1379 writes `last_activity` (new impl)
   - Confirm `ha_on_primary_ctrl_fd_rdhup` now calls `ha_disarm_heartbeat_timeout_vtask` as its first step (Req 5.4)

src/controller/testsuite/test_ha_liveness.c

@@ -576,6 +576,64 @@ static void test_cluster_dispatch_ctrlhello_resets_activity_when_standby(void)
     printf("test_cluster_dispatch_ctrlhello_resets_activity_when_standby: PASS\n");
 }
 
+/* ── Test 14: ha_arm_heartbeat_timeout_vtask does not increase thread count ── */
+
+/*
+ * Task 3.2, Req 1.6: ha_arm_heartbeat_timeout_vtask must NOT spawn a pthread.
+ *
+ * We read the process thread count from /proc/self/status before and after
+ * calling the arm function and assert the count is unchanged.  This is a
+ * stronger check than test_ha_arm_no_crash_no_thread (Test 6), which only
+ * verifies no crash and last_activity written.
+ *
+ * Note: with c==NULL the delaymgr is not running; delay_task_ms will fail
+ * silently (no actual delaymgr task is queued), but the arm path executes and
+ * must not create a thread as a side-effect.
+ */
+static int read_proc_thread_count(void)
+{
+    FILE *f = fopen("/proc/self/status", "r");
+    if (!f) return -1;
+    char line[128];
+    int count = -1;
+    while (fgets(line, sizeof(line), f)) {
+        if (strncmp(line, "Threads:", 8) == 0) {
+            if (sscanf(line + 8, "%d", &count) != 1)
+                count = -1;
+            break;
+        }
+    }
+    fclose(f);
+    return count;
+}
+
+static void test_ha_arm_does_not_increase_thread_count(void)
+{
+    ha_state_t ha;
+    TEST_ASSERT_EQUAL_INT(0, ha_init(&ha, &g_cfg, 1));
+    ha_do_demote(&ha);
+
+    int threads_before = read_proc_thread_count();
+    TEST_ASSERT_NOT_EQUAL_MESSAGE(-1, threads_before,
+        "could not read /proc/self/status Threads");
+
+    /* Call arm — must not spawn a pthread (Req 1.6) */
+    ha_arm_heartbeat_timeout_vtask(&ha, NULL);
+
+    int threads_after = read_proc_thread_count();
+    TEST_ASSERT_NOT_EQUAL_MESSAGE(-1, threads_after,
+        "could not read /proc/self/status Threads after arm");
+
+    TEST_ASSERT_EQUAL_INT_MESSAGE(threads_before, threads_after,
+        "Req 1.6: ha_arm_heartbeat_timeout_vtask must not spawn a pthread");
+
+    /* Disarm to release the ctx allocation */
+    ha_disarm_heartbeat_timeout_vtask(&ha);
+
+    ha_fini(&ha);
+    printf("test_ha_arm_does_not_increase_thread_count: PASS\n");
+}
+
 /* ── Suite entry point ──────────────────────────────────────────────────── */
 
 void test_ha_liveness(void)
@@ -594,5 +652,6 @@ void test_ha_liveness(void)
     RUN_TEST(test_cluster_dispatch_nop_resets_activity_when_standby);
     RUN_TEST(test_cluster_dispatch_nop_skips_when_primary);
     RUN_TEST(test_cluster_dispatch_ctrlhello_resets_activity_when_standby);
+    RUN_TEST(test_ha_arm_does_not_increase_thread_count);
     UNITY_END();
 }