fix(ncm §32): 内存瘦身修 OOM 被杀 —— 封面降采样(8.28MB→0.78MB) + 瞬态 rbuf 缩减 + 线程栈显式

真机 dmesg 实锤：OOM Kill ncm (score 460, anon-rss 26.9MB, 设备 56MB)。
画像：封面全分辨率 RGBA 8.28MB(1448x1448 原生解码驻留) 是最大可控块。

瘦身（按收益排序）：
1. sdk meow_ui_img 新增纯增量 meow_img_downscale + cover.c cover_cap(≤480px)
   → 封面 8.28MB→0.78MB，-7.65MB（mem_sim 实测 PASS）。
2. ncm_api.c 瞬态响应 rbuf：song_url→64KB、lyric/song_detail/cloudsearch/user_playlist→256KB
   （detail/track_all 保 1MB）。
3. ncm_app_internal.h 新增 ncm_thread_create（显式 128KB 栈），替换全部 14 处 pthread_create。
4. 滑动窗口/meta 复核零回退（window_sim：608B/首，6000 首 280KB 恒定）。

验证：mem_sim 封面收益 PASS + host home/player 渲染 OK + stream_sim/player_flow_sim/
window_sim/search_sim/cache_evict_sim 全 PASS + test_ncm_core host+mipsel(qemu) PASS
+ build_ncm.sh -Wall -Wextra 0 warning。真机 scp 播放在跑确认（缓存曲，0 播放请求）。

新 ncm md5 44fa16fe（text 1015150/bss 1362500）。正式部署留主会话。

patch_v2/ncm_app/app/ui/home.c

@@ -233,7 +233,7 @@ void home_reload(void)
         g_home_loading = 1;
     }
     g_home_thr_on = 1;
-    if (pthread_create(&g_home_thr, NULL, home_worker, NULL) != 0) {
+    if (ncm_thread_create(&g_home_thr, home_worker, NULL) != 0) {
         g_home_thr_on = 0; g_home_loading = 0; g_load_err = NCM_ERR_IO;
     }
     home_apply();

patch_v2/ncm_app/app/ui/login.c

@@ -176,7 +176,7 @@ int login_start(void)
     g_polling = 1;
     g_done = 0;
     g_err = 0;
-    if (pthread_create(&g_thread, NULL, login_worker, NULL) != 0) {
+    if (ncm_thread_create(&g_thread, login_worker, NULL) != 0) {
         g_polling = 0;
         return -1;
     }

patch_v2/ncm_app/app/ui/playlist.c

@@ -306,7 +306,7 @@ static void pl_maybe_ensure(void)
     g_ens_first = 0;
     g_plloading = 1;
     g_plthr_on = 1;
-    if (pthread_create(&g_plthr, NULL, playlist_worker, NULL) != 0) {
+    if (ncm_thread_create(&g_plthr, playlist_worker, NULL) != 0) {
         g_plthr_on = 0; g_plloading = 0; ncm_snack("加载失败");
     }
 }
@@ -340,7 +340,7 @@ void playlist_refresh(void)
     g_pl_stale = 0;
     g_plloading = 1;
     g_plthr_on = 1;
-    if (pthread_create(&g_plthr, NULL, playlist_worker, NULL) != 0) {
+    if (ncm_thread_create(&g_plthr, playlist_worker, NULL) != 0) {
         g_plthr_on = 0; g_plloading = 0; g_load_err = NCM_ERR_IO;
     }
     pl_apply(1);

patch_v2/ncm_app/app/ui/search.c

@@ -211,7 +211,7 @@ static void sr_maybe_load_more(void)
     g_req_tab = g_tab; g_req_offset = n; g_req_replace = 0;
     /* 单飞：无 worker 才发（search_worker 尾部解锁） */
     g_thr_on = 1; g_loading = 1; g_more_err = 0;
-    if (pthread_create(&g_thr, NULL, search_worker, NULL) != 0) {
+    if (ncm_thread_create(&g_thr, search_worker, NULL) != 0) {
         g_thr_on = 0; g_loading = 0; g_more_err = 1;
     }
 }
@@ -270,7 +270,7 @@ void search_submit(const char *kw)
     g_st.search_err = 0;
     g_loading = 1; g_more_err = 0;
     g_thr_on = 1;
-    if (pthread_create(&g_thr, NULL, search_worker, NULL) != 0) {
+    if (ncm_thread_create(&g_thr, search_worker, NULL) != 0) {
         g_thr_on = 0; g_loading = 0; g_st.search_err = NCM_ERR_IO;
     }
     sr_apply();
@@ -290,7 +290,7 @@ static void sr_set_tab(int t)
         g_req_tab = g_tab; g_req_offset = 0; g_req_replace = 1;
         g_loading = 1; g_more_err = 0;
         g_thr_on = 1;
-        if (pthread_create(&g_thr, NULL, search_worker, NULL) != 0) {
+        if (ncm_thread_create(&g_thr, search_worker, NULL) != 0) {
             g_thr_on = 0; g_loading = 0;
         }
     }
@@ -354,7 +354,7 @@ int search_on_tap(int x, int y)
                     g_req_tab = g_tab; g_req_offset = 0; g_req_replace = 1;
                     g_loading = 1;
                     g_thr_on = 1;
-                    if (pthread_create(&g_thr, NULL, search_worker, NULL) != 0) {
+                    if (ncm_thread_create(&g_thr, search_worker, NULL) != 0) {
                         g_thr_on = 0; g_loading = 0; g_st.search_err = NCM_ERR_IO;
                     }
                 }