ncm: FLAC 解码落地(dr_flac 0.13.4 单头入库) + 缓存键=歌曲ID+音质档位

- 解码分发 decoder.c：magic(fLaC→dr_flac / 其它→minimp3)；flac ≤16bit→S16、
  >16bit→S32 满幅送 audiod(AUDIO_FMT_S32)，rate/ch/bits 按实际流，零 SRC 零裁剪
- song_url_auto 接受 flac（type 权威/url 扩展名兜底），降级语义不变；flac 下载限幅 1GB
- 缓存键 song_<id>_<level>.<ext>：同歌同档命中不重下，换档新条目旧档留 LRU；
  ext 前导点正名(修双点名)，lookup 回退历史双点名+旧无档键温和兼容
- audio_out S32 通路（AUDIOD/ALSA/WAV）+ 流死重开按 bits 还原格式
- 验证(0 真实请求)：44.1k/16 与 96k/24 自制样本宿主+qemu 帧数/时长精确、
  逐样本零误差；mp3 回归逐帧一致；player_flow_sim P1-P6(新 P6 档位键/flac ext)、
  cache_evict/cover/pagination/window/audiod_chain sim 全 PASS；mipsel 0 warning
- REPORT §19 / VENDOR_NOTES dr_flac 条目；未部署真机（留主会话）

patch_v2/ncm_app/build_ncm.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
-# build_ncm.sh — 构建 dev.player.ncm（网易云 App，SDK framework=1）：链 meow_ui.a + 核心库 + minimp3 + mbedtls。
-# 静态 MIPS32r2 (musl sf)。自有代码（app/ + core/）+ core 支撑 vendor 编译；vendor/minimp3/qrcodegen/jsmn 豁免告警。
+# build_ncm.sh — 构建 dev.player.ncm（网易云 App，SDK framework=1）：链 meow_ui.a + 核心库 + minimp3 + dr_flac + mbedtls。
+# 静态 MIPS32r2 (musl sf)。自有代码（app/ + core/）+ core 支撑 vendor 编译；vendor/minimp3/dr_flac/qrcodegen/jsmn 豁免告警。
 # 仅改本 App 目录；编译期不改 SDK（patch_v2/sdk/）、不动 meow_launcherd/。mipsel -Wall -Wextra 0 warning。
 set -e
 cd "$(dirname "$0")"
@@ -11,7 +11,7 @@ OUT="$PWD/out"
 mkdir -p "$OUT/app-mipsel"
 
 INC="-Icore -I../sdk -I../meow_launcherd \
-     -Ivendor/mbedtls/include -Ivendor/jsmn -Ivendor/qrcodegen/c -Ivendor/minimp3"
+     -Ivendor/mbedtls/include -Ivendor/jsmn -Ivendor/qrcodegen/c -Ivendor/minimp3 -Ivendor/dr_flac"
 STRICT="-Wall -Wextra -Os -DJSMN_HEADER"
 
 CORE="core/ncm_common.c core/ncm_json.c core/ncm_store.c core/ncm_http.c \
@@ -21,7 +21,7 @@ APP="app/app.c app/ui/login.c app/ui/home.c app/ui/playlist.c app/ui/player.c \
     app/ui/settings.c app/ui/search.c app/ui/ncm_colors.c app/ui/chrome.c \
     app/logic/appstate.c app/logic/lyric.c app/logic/songmeta.c \
     app/logic/cover.c app/play/player_manager.c app/play/audio_out.c \
-    app/play/ipc_media.c app/play/minimp3_impl.c"
+    app/play/ipc_media.c app/play/decoder.c app/play/minimp3_impl.c"
 
 echo "==> app+core (strict)"
 for f in $APP $CORE; do
@@ -31,6 +31,7 @@ done
 
 echo "==> vendor impl (warn-exempt)"
 $CC -static -c -Os -I../meow_launcherd -Ivendor/minimp3 app/play/minimp3_impl.c -o "$OUT/app-mipsel/minimp3_impl.o"
+$CC -static -c -Os -Ivendor/dr_flac app/play/dr_flac_impl.c -o "$OUT/app-mipsel/dr_flac_impl.o"
 $CC -static -c -Os -Ivendor/jsmn core/jsmn_impl.c -o "$OUT/app-mipsel/jsmn_impl.o"
 $CC -static -c -Os -Ivendor/qrcodegen/c vendor/qrcodegen/c/qrcodegen.c -o "$OUT/app-mipsel/qrcodegen.o"