fix(sdk/watchdog): 236 收尾 — sigusr1_guard 无日志目录时落 stderr 可观测; test_wd_fw 补 fw-app/裸沉浸/裸非沉浸三用例; hello/files/ncm 随 meow_ui.a(4020227c) 重链 (已热更到卡, watchdog 6373d8e5 待入 M2.89)

patch_v2/sdk/meow_ui_log.c

@@ -154,11 +154,12 @@ static void sigusr1_guard(int sig)
 {
     (void)sig;
     if (!g_log_open_tried) { g_log_open_tried = 1; log_open(); }
-    if (g_log_fd >= 0) {
-        char line[128];
-        int n = snprintf(line, sizeof line, "%llu [%s] WARN sigusr1: ignored (guard)\n",
-                         (unsigned long long)meow_ui_time_ms(), g_app_id);
-        if (n > 0) { ssize_t w = write(g_log_fd, line, (size_t)n); (void)w; }
+    char line[128];
+    int n = snprintf(line, sizeof line, "%llu [%s] WARN sigusr1: ignored (guard)\n",
+                     (unsigned long long)meow_ui_time_ms(), g_app_id);
+    if (n > 0) {
+        if (g_log_fd >= 0) { ssize_t w = write(g_log_fd, line, (size_t)n); (void)w; }
+        else { ssize_t w = write(2, line, (size_t)n); (void)w; }   /* 无日志目录：写 stderr，护栏可观测 */
     }
     /* 不 exit、不返回处理：返回交给 on_swipe/SDK。这里仅记录并吞掉。 */
 }