fix(ncm §20.3): 降级链账户/fee感知 auto_av —— 修「SQ 被跳过掉标准」（297）

根因：ncm_api_song_url_auto 无账户感知，依赖调用方按会员钳顶；若账户 VIP 态未就绪/
错钳到 EXHIGH，降级链从 EXHIGH 起步，LOSSLESS(无损 SQ) 被跳过，直接掉「标准」。
修法：新增 ncm_api_song_url_auto_av[_f]（§20.3 权威形态）：fee∈{1,4} 且非 CVIP →
NCM_ERR_VIP 零请求；按 account_vip 自钳顶(NONE→EXHIGH/CVIP→HIRES/SVIP→SURROUND)；
只试账户可访问档(ncm_api_level_gate<=vip)；落在最近可用档。原 auto/auto_f 行为零回归。
逐级尝试重构为共享 level_attempt（type/url 接受+静默降档采信）。
测试(bench/degrade_sim.c)：fee门禁5例 + auto_av矩阵 vip3×desired9×avail9=243例全PASS
+ 真机复现(CVIP+Hi-Res+有SQ无HiRes→落无损SQ flac)；原90例零回归。
验证：test_ncm_core_host+qemu-mipsel 全PASS；build_core/build_ncm -Wall -Wextra 0 warning。
新 ncm md5 1064a1d686390cc159f18296ee2980ee（未部署，留主会话）。
遗留：player_manager.c 仍调 auto（不传vip/fee），应改请 auto_av(account_vip()+fee)；
真机若仍掉标准需另查旧缓存 song_<id>_hires.mp3 复用或旧二进制。

patch_v2/ncm_app/bench/degrade_sim.c

@@ -66,6 +66,34 @@ static int total_calls(void)
     return n;
 }
 
+/* ---- §20.3 账户/fee 感知降级链（auto_av_f）期望模型 ----
+ * cap(vip)：NONE→EXHIGH / CVIP→HIRES / SVIP→SURROUND（与 account.c account_level_cap 同口径）。
+ * start = clamp(desired, STANDARD, cap)；只试 gate(lv)<=vip 的档；落在 lv<=avail 的最近可用档。 */
+static int cap_for_vip(int vip) {
+    switch (vip) {
+        case NCM_VIP_SVIP: return NCM_LEVEL_SURROUND;
+        case NCM_VIP_CVIP: return NCM_LEVEL_HIRES;
+        default:           return NCM_LEVEL_EXHIGH;
+    }
+}
+static int expect_land(int vip, int desired, int avail) {
+    int cap = cap_for_vip(vip);
+    int start = desired > cap ? cap : desired;
+    if (start < NCM_LEVEL_STANDARD) start = NCM_LEVEL_STANDARD;
+    for (int lv = start; lv >= NCM_LEVEL_STANDARD; lv--)
+        if (ncm_api_level_gate(lv) <= vip && lv <= avail) return lv;
+    return -1;
+}
+static int expect_tried(int vip, int desired, int best) {
+    int cap = cap_for_vip(vip);
+    int start = desired > cap ? cap : desired;
+    if (start < NCM_LEVEL_STANDARD) start = NCM_LEVEL_STANDARD;
+    int n = 0;
+    for (int lv = start; lv >= NCM_LEVEL_STANDARD; lv--)
+        if (ncm_api_level_gate(lv) <= vip && (best < 0 || lv >= best)) n++;
+    return n;
+}
+
 int main(void)
 {
     ncm_play_url_t u;
@@ -160,6 +188,63 @@ int main(void)
           "req surround, resp level=sky (歧义) -> eff=surround (got %d)", eff);
     g_resp_level = NULL;
 
+    printf("== 7) auto_av_f fee 门禁（§20.4：fee∈{1,4} 且非 CVIP → 零请求 NCM_ERR_VIP）==\n");
+    reset_calls(); g_avail_from = NCM_LEVEL_SURROUND; g_type = "mp3";
+    CHECK(ncm_api_song_url_auto_av_f("d", "c", "1", NCM_VIP_NONE, 1, NCM_LEVEL_HIRES, &u, &eff, fake_try)
+              == NCM_ERR_VIP && total_calls() == 0,
+          "fee=1 + NONE -> NCM_ERR_VIP (calls=%d)", total_calls());
+    CHECK(ncm_api_song_url_auto_av_f("d", "c", "1", NCM_VIP_NONE, 4, NCM_LEVEL_HIRES, &u, &eff, fake_try)
+              == NCM_ERR_VIP && total_calls() == 0,
+          "fee=4 + NONE -> NCM_ERR_VIP (calls=%d)", total_calls());
+    CHECK(ncm_api_song_url_auto_av_f("d", "c", "1", NCM_VIP_CVIP, 1, NCM_LEVEL_HIRES, &u, &eff, fake_try)
+              == NCM_OK, "fee=1 + CVIP -> 放行");
+    CHECK(ncm_api_song_url_auto_av_f("d", "c", "1", NCM_VIP_NONE, 8, NCM_LEVEL_HIRES, &u, &eff, fake_try)
+              == NCM_OK, "fee=8 + NONE -> 放行（免费听低音质）");
+    CHECK(ncm_api_song_url_auto_av_f("d", "c", "1", NCM_VIP_NONE, 0, NCM_LEVEL_HIRES, &u, &eff, fake_try)
+              == NCM_OK, "fee=0 + NONE -> 放行");
+
+    printf("== 8) auto_av_f 全矩阵: account_vip 3 x desired 9 x avail 9（钳顶+门槛+最近可用档）==\n");
+    int av_bad = 0, av_cases = 0;
+    for (int vip = NCM_VIP_NONE; vip <= NCM_VIP_SVIP; vip++) {
+        for (int desired = NCM_LEVEL_STANDARD; desired <= NCM_LEVEL_SURROUND; desired++) {
+            for (int avail = NCM_LEVEL_STANDARD; avail <= NCM_LEVEL_SURROUND; avail++) {
+                reset_calls();
+                g_avail_from = avail; g_type = "mp3";
+                int rc = ncm_api_song_url_auto_av_f("dev", "ck", "1", vip, 0, desired, &u, &eff, fake_try);
+                int want = expect_land(vip, desired, avail);
+                int ok = (want >= 0 && rc == NCM_OK && eff == want && u.url[0] &&
+                          total_calls() == expect_tried(vip, desired, want));
+                av_cases++;
+                if (!ok) {
+                    av_bad++;
+                    printf("  FAIL  vip=%d desired=%d(%s) avail=%d -> rc=%d eff=%d calls=%d (want %d/%d)\n",
+                           vip, desired, ncm_api_level_str(desired), avail, rc, eff, total_calls(),
+                           want, expect_tried(vip, desired, want));
+                    g_fail = 1;
+                }
+            }
+        }
+    }
+    CHECK(av_bad == 0, "auto_av matrix %d cases all pass (vip 3 x desired 9 x avail 9)", av_cases);
+
+    printf("== 9) 真机场景复现：CVIP + 设置Hi-Res + 歌曲「有SQ无Hi-Res」→ 落无损SQ ==\n");
+    reset_calls();
+    g_avail_from = NCM_LEVEL_LOSSLESS;   /* 歌曲只提供到 SQ（及更低）→ 无 Hi-Res */
+    g_type = "flac";                     /* SQ 以 flac 下发 */
+    int rc9 = ncm_api_song_url_auto_av_f("d", "c", "10", NCM_VIP_CVIP, 0, NCM_LEVEL_HIRES,
+                                         &u, &eff, fake_try);
+    CHECK(rc9 == NCM_OK && eff == NCM_LEVEL_LOSSLESS && strcmp(u.type, "flac") == 0,
+          "CVIP Hi-Res、有SQ无HiRes -> 落无损SQ (rc=%d eff=%d(%s) type=%s)",
+          rc9, eff, ncm_api_level_str(eff), u.type);
+    /* 对照：若账户VIP态未就绪(NONE)，钳顶把Hi-Res压到极高，SQ被跳过（旧app clamp即此路径） */
+    reset_calls();
+    g_avail_from = NCM_LEVEL_LOSSLESS; g_type = "flac";
+    int rcn = ncm_api_song_url_auto_av_f("d", "c", "10", NCM_VIP_NONE, 0, NCM_LEVEL_HIRES,
+                                         &u, &eff, fake_try);
+    CHECK(rcn == NCM_OK && eff == NCM_LEVEL_EXHIGH,
+          "NONE+Hi-Res -> 钳到极高EXHIGH (rc=%d eff=%d) — 旧app clamp正是此路径致SQ被跳过",
+          rcn, eff);
+
     printf(g_fail ? "== DEGRADE SIM: FAIL ==\n" : "== DEGRADE SIM: ALL PASS ==\n");
     return g_fail;
 }