fix(npc): gateway scene notify non-blocking

The scene->gateway POST ran synchronously (2 s timeout) on the scene
transition, so an offline gateway lagged EVERY scene change by 2 s.
Fire it on a detached one-shot task instead, so the game's scene
transitions never wait on the network. Frees the heap scene copy and
self-deletes. Builds clean.

idf_zacus/components/npc_engine/npc_engine.c

@@ -17,11 +17,14 @@
 #include "npc_engine.h"
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "esp_err.h"
 #include "esp_http_client.h"
 #include "esp_log.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
 
 #include "media_manager.h"
 #include "hints_client.h"
@@ -39,11 +42,12 @@ void npc_engine_set_gateway(const char *base_url, const char *token) {
     if (token)    snprintf(s_gw_token, sizeof(s_gw_token), "%s", token);
 }
 
-// Fire a one-shot POST {gateway}/game/step?scene=<scene>. Short timeout,
-// best-effort: the puzzle progresses fine without it, it only keeps the phone
-// NPCs' hints in sync with the current scene. Never propagates failure.
-static void notify_gateway_scene(const char *scene) {
-    if (!s_gw_url[0] || !scene || !scene[0]) return;
+// One-shot worker: POST {gateway}/game/step?scene=<scene> then self-delete.
+// Runs on its own task so a slow/unreachable gateway NEVER stalls the scene
+// transition (the game must not lag 2 s on every scene change if the gateway is
+// offline). `arg` is a heap copy of the scene, freed here. Best-effort.
+static void gw_notify_task(void *arg) {
+    char *scene = (char *) arg;
     char url[256];
     snprintf(url, sizeof(url), "%s/game/step?scene=%s", s_gw_url, scene);
     esp_http_client_config_t cfg = {
@@ -52,20 +56,37 @@ static void notify_gateway_scene(const char *scene) {
         .timeout_ms = 2000,
     };
     esp_http_client_handle_t cli = esp_http_client_init(&cfg);
-    if (!cli) return;
-    if (s_gw_token[0]) {
-        char auth[112];
-        snprintf(auth, sizeof(auth), "Bearer %s", s_gw_token);
-        esp_http_client_set_header(cli, "Authorization", auth);
+    if (cli) {
+        if (s_gw_token[0]) {
+            char auth[112];
+            snprintf(auth, sizeof(auth), "Bearer %s", s_gw_token);
+            esp_http_client_set_header(cli, "Authorization", auth);
+        }
+        esp_err_t err = esp_http_client_perform(cli);
+        if (err != ESP_OK) {
+            ESP_LOGW(TAG, "gateway /game/step notify failed: %s", esp_err_to_name(err));
+        } else {
+            ESP_LOGI(TAG, "gateway scene -> %s (HTTP %d)", scene,
+                     esp_http_client_get_status_code(cli));
+        }
+        esp_http_client_cleanup(cli);
     }
-    esp_err_t err = esp_http_client_perform(cli);
-    if (err != ESP_OK) {
-        ESP_LOGW(TAG, "gateway /game/step notify failed: %s", esp_err_to_name(err));
-    } else {
-        ESP_LOGI(TAG, "gateway scene -> %s (HTTP %d)", scene,
-                 esp_http_client_get_status_code(cli));
+    free(scene);
+    vTaskDelete(NULL);
+}
+
+// Fire-and-forget the gateway scene notification on a detached task so a scene
+// change is never blocked by the network. No-op if no gateway configured.
+static void notify_gateway_scene(const char *scene) {
+    if (!s_gw_url[0] || !scene || !scene[0]) return;
+    size_t n = strlen(scene) + 1;
+    char *copy = malloc(n);
+    if (!copy) return;
+    memcpy(copy, scene, n);
+    if (xTaskCreate(gw_notify_task, "gw_notify", 4096, copy, 3, NULL) != pdPASS) {
+        ESP_LOGW(TAG, "gw_notify task spawn failed");
+        free(copy);
     }
-    esp_http_client_cleanup(cli);
 }
 
 // ─── Core: scene/trigger/mood lookup tables (verbatim Arduino) ──────────────