feat(sdk+launcher): SDK nav/media封装 + §10.5 App前台唤起通知中心 (agent-206) — meow_ui_nav.c(env栈初始化+report/request_exit) + meow_ui_media.c(懒连断线重连, meta上报+playctl接收) + MSG_NOTIF_OPEN=0x28/CLOSE=0x29(0x25/26已被占); SDK顶部下滑手势→IPC; launcher App前台会话叠加通知中心(SIGSTOP→读帧→接管输入→恢复SIGCONT, 面板内App崩溃即关); hello接线验证

meow_ui.a→9a8eb7ef; hello→fc299577; launcher→b33da20a; 宿主5套件+新test_notif_open+qemu分发 全过
出入: SDK符号用meow_ui_前缀防与launcher内同名冲突; 叠加会话真机待验; §10.5文档旧号段已过时

patch_v2/sdk/meow_ui_activity.c

@@ -31,3 +31,8 @@ int meow_ui_activity_active(void)
 {
     return g_act_n > 0 ? g_act[g_act_n - 1] : 0;
 }
+
+int meow_ui_activity_depth(void)
+{
+    return g_act_n;
+}