ncm 三期三批: 歌曲对象瘦身(1324→608B)+滑动窗口(NCM_SONG_WINDOW=256, 取消1000截断支撑任意长度歌单)+播放快照解耦 — agent-251

- core/ncm_api.h: ncm_song_t 瘦身 id24/name128/art96/al96/pic256/dt int32 (1324B→608B)
- appstate.c 滑动窗口: song_ids 全量 trackIds 索引(16384) + songs[256] 窗口感知
  (song_valid 位图/window_base/滑窗 memmove 保留重叠), ensure_range 批网格(100)对齐
  预取, songmeta.c 盘缓存 <cache_dir>/meta/<id>.bin (回滚/二次进入 0 网络请求)
- playlist.c 触底分页退役→视口 ensure(±24 行), 占位行可直点(播放线程 fetch 物化),
  footer 改视口区间/总数
- 播放兼容: g_play.play_song 快照(mu), run_song 起播物化后全链路(下载/歌词/IPC META/
  播放页 UI)读快照——窗口滑出当前播放曲不崩; 边界 song_count→track_ids_count
- 验证(0 真实请求): pagination_sim 全 PASS(5191 无截断/52 批); window_sim 6000 首
  全程下滚 750 步视口全物化/song_detail 恰 60 次/回滚+0 请求/播放 fetch 不滑窗;
  core 宿主+qemu 全 PASS; mipsel -Wall -Wextra 0 warning, bss 2052068→1080900(-47%)
- 未部署真机(设备音频线排查中, 部署留主会话)

patch_v2/ncm_app/app/test/test_ncm_app.c

@@ -42,7 +42,9 @@ static void mock_songs(void)
                                 "Song Four", "Song Five", "Song Six" };
     static const char *ar[] = { "Artist A", "Artist B", "Artist C",
                                 "Artist D", "Artist E", "Artist F" };
-    g_st.song_count = 6;
+    g_st.song_count = 6;             /* 滑窗模型：窗口 base=0，6 槽全有效（§17） */
+    g_st.window_base = 0;
+    g_st.track_ids_count = 6;
     g_st.active_playlist = 0;
     for (int i = 0; i < 6; i++) {
         snprintf(g_st.songs[i].id, sizeof g_st.songs[i].id, "%ld", 1000L + i);
@@ -51,6 +53,8 @@ static void mock_songs(void)
         snprintf(g_st.songs[i].album_name, sizeof g_st.songs[i].album_name, "Album %d", i + 1);
         g_st.songs[i].duration_ms = 180000 + i * 20000;
         g_st.songs[i].fee = (i == 3) ? 1 : 0;
+        g_st.song_valid[i] = 1;
+        g_st.song_ids[i] = 1000 + i;
     }
     ncm_strlcpy(g_st.cover_url, "http://p1.music.126.net/cover0.jpg", sizeof g_st.cover_url);
     g_st.playing_song = 0;
@@ -139,6 +143,8 @@ int main(int argc, char **argv)
         g_play.cur_song = 0;
         g_play.pos_ms = 94000;
         g_play.dur_ms = 180000;
+        g_play.play_song = g_st.songs[0];   /* 播放快照（§17） */
+        g_play.play_song_valid = 1;
         pthread_mutex_unlock(&g_play.mu);
     } else if (strcmp(name, "settings") == 0) {
         g_st.logged_in = 1;
@@ -162,8 +168,11 @@ int main(int argc, char **argv)
             snprintf(g_st.songs[i].album_name, sizeof g_st.songs[i].album_name, "%s", al[i]);
             g_st.songs[i].duration_ms = 180000 + i * 20000;
             g_st.songs[i].fee = 0;
+            g_st.song_valid[i] = 1;
+            g_st.song_ids[i] = 1000 + i;
         }
         g_st.song_count = 3;
+        g_st.track_ids_count = 3;
     } else {
         mock_playlists();
     }