feat(bt): 批①后台常驻框架实施 — meow_media_app_resident按app会话判活跃+should_keep三参(keepalive||bg_audio&&resident)+background_keepalive声明解析透传+amsd EV BG/FG上报;宿主test_media39/test_bgplay/test_bg_keep19全过,0warning;落盘APP_BACKGROUND_KEEPALIVE_P1;降配(nice)待真机未做

patch_v2/meow_amsd/meow_amsd.c

@@ -956,6 +956,41 @@ static void handle_out(char **t, int nt)
     out_append(pkg, pid, epoch, up, text);
 }
 
+/* 批①后台常驻上报（单向 best-effort，launcher → amsd）：
+ *   EV BG <app> <pid>  → AMS_BG（转后台保活）
+ *   EV FG <app>        → AMS_FG（回前台）。旧 launcher 不发、本层不识别也不崩。 */
+static void handle_bg(char **t, int nt)
+{
+    if (nt < 2) return;
+    const char *pkg = t[0];
+    pid_t pid = (pid_t)atoi(t[1]);
+    long epoch = (nt > 2) ? atol(t[2]) : (long)time(NULL);
+    long up = (nt > 3) ? atol(t[3]) : read_uptime_sec();
+    struct ams_app *a = app_get(pkg);
+    if (!a) return;
+    a->state = AMS_BG;
+    a->pid = pid;
+    char detail[192];
+    snprintf(detail, sizeof detail, "pid=%ld", (long)pid);
+    hist_push(a, "bg", detail, epoch, up);
+    emit_log("BG %s pid=%ld", pkg, (long)pid);
+}
+
+static void handle_fg(char **t, int nt)
+{
+    if (nt < 1) return;
+    const char *pkg = t[0];
+    long epoch = (nt > 1) ? atol(t[1]) : (long)time(NULL);
+    long up = (nt > 2) ? atol(t[2]) : read_uptime_sec();
+    struct ams_app *a = app_find(pkg);
+    if (!a) return;
+    a->state = AMS_FG;
+    char detail[192];
+    snprintf(detail, sizeof detail, "bg->fg");
+    hist_push(a, "fg", detail, epoch, up);
+    emit_log("FG %s", pkg);
+}
+
 /* ---- §6.2 二期：picker 编排（amsd 路由权威） ---- */
 
 static struct ams_picker *picker_find(const char *action)
@@ -1252,6 +1287,8 @@ static int dispatch_line(char *line, char *resp, int rn)
         if (!strcmp(tok[0], "LAUNCH")) { handle_launch(tok + 1, nt - 1); }
         else if (!strcmp(tok[0], "EXIT"))  { handle_exit(tok + 1, nt - 1); }
         else if (!strcmp(tok[0], "OUT"))   { handle_out(tok + 1, nt - 1); }
+        else if (!strcmp(tok[0], "BG"))    { handle_bg(tok + 1, nt - 1); }
+        else if (!strcmp(tok[0], "FG"))    { handle_fg(tok + 1, nt - 1); }
         return 0;
     }