app.json 二进制依赖 depends：启动前检查（launcher）+ 安装提示（nyai）

需求（用户定案）：App 复杂功能若依赖现成 Linux 二进制（板载 /usr/bin 或卡上
MeowOS/opt/bin）能效更好，声明后系统启动 App 前检查依赖是否存在。

- depends 行式声明：depends=curl,jq:optional,ffmpeg:required（无标注默认
  required；也接受 :opt/:req；未知修饰符按 required 处理并 WARN；空项/超量丢弃）
- launch_app_chain 冷启动时按序查 /usr/bin/<name> 与 <卡>/MeowOS/opt/bin/<name>
  （X_OK，两类命中即满足）；缺 required → 不启动（toast「缺依赖: <name>」+ 日志，
  沿用 CANNOT START 风格）；optional 缺失 → 仅 WARN 放行；只在启动时查，不做周期复查
- nyai install 对包内 app.json depends 同查并提示（不阻断安装，缺 required 标注
  「安装后启动将失败」）
- 新增 meow_dep.c（独立 TU，解析/检查/块原因），宿主测试 test_depends.c
  解析矩阵 12 用例 + 假根检查路径 12 用例全 PASS；launcher/nyai mipsel 交叉
  -Wall -Wextra 0 warning；launcher 现有宿主测试回归全过
- 文档：APPS.md §2.1 字段表 + docs/MEOWOS_SPEC_REF.md §5.5 同步；hello app.json
  加 depends:curl:optional 示例

launcher md5 899ac22c10f596909d7f35ea685744de（fw_content.conf 已更新；/usr/bin
只读，留给主会话打包固件）

patch_v2/meow_launcherd/main_menu.c

@@ -13,6 +13,16 @@
 int menu_opened_blank = 0;
 
 
+/* launch_app/launch_activity 返回 -1 时的 toast：缺二进制依赖（app.json depends）→ 「缺依赖: <name>」；
+ * 其余启动失败沿用「CANNOT START: <name>」。原因由 meow_dep.c 的 meow_dep_block_reason() 提供。 */
+static void launch_fail_toast(char *toast, size_t n, const char *name)
+{
+    const char *bd = meow_dep_block_reason();
+    if (bd && bd[0]) snprintf(toast, n, "缺依赖: %s", bd);
+    else             snprintf(toast, n, "CANNOT START: %s", name);
+}
+
+
 /* ---- config (MeowAPPs/meow.conf): pure black background by default ---- */
 uint32_t menu_bg = 0x000000;
 
@@ -904,7 +914,7 @@ static void run_menu(struct app apps[MAX_APPS], int napps, int state,
                             ret = launch_app(&apps[idx]);
                         }
                         if (ret != 0) {
-                            snprintf(toast, sizeof toast, "CANNOT START: %s", apps[idx].name);
+                            launch_fail_toast(toast, sizeof toast, apps[idx].name);
                             toast_ms = TOAST_MS;
                         }
                         menu_after_app_exit(ret == 0);
@@ -938,7 +948,7 @@ static void run_menu(struct app apps[MAX_APPS], int napps, int state,
                 last_input_ms = now_ms();   /* M2.17：回主界面即视为输入，重置自动息屏计时 */
                 dirty = 1;   /* app wrote buffer0 during its run -> redraw menu */
                 if (ret != 0) {
-                    snprintf(toast, sizeof toast, "CANNOT START: %s", apps[0].name);
+                    launch_fail_toast(toast, sizeof toast, apps[0].name);
                     toast_ms = TOAST_MS;
                 }
             } else {
@@ -1297,8 +1307,7 @@ static void run_menu(struct app apps[MAX_APPS], int napps, int state,
                                 last_input_ms = now_ms();
                                 dirty = 1;
                                 if (ret != 0) {
-                                    snprintf(toast, sizeof toast, "CANNOT START: %s",
-                                             apps[click.app_idx].name);
+                                    launch_fail_toast(toast, sizeof toast, apps[click.app_idx].name);
                                     toast_ms = TOAST_MS;
                                 }
                             } else if (click.status == NOTIF_CLICK_STATUS_NOROUTE) {
@@ -1392,8 +1401,7 @@ static void run_menu(struct app apps[MAX_APPS], int napps, int state,
                                         last_input_ms = now_ms();
                                         dirty = 1;
                                         if (ret != 0) {
-                                            snprintf(toast, sizeof toast, "CANNOT START: %s",
-                                                     apps[click.app_idx].name);
+                                            launch_fail_toast(toast, sizeof toast, apps[click.app_idx].name);
                                             toast_ms = TOAST_MS;
                                         }
                                     } else if (click.status == NOTIF_CLICK_STATUS_NOROUTE) {
@@ -1497,7 +1505,7 @@ static void run_menu(struct app apps[MAX_APPS], int napps, int state,
                                             last_input_ms = now_ms();   /* M2.17：回主界面即视为输入，重置自动息屏计时 */
                                             dirty = 1;   /* app wrote buffer0 -> redraw menu */
                                             if (ret != 0) {
-                                                snprintf(toast, sizeof toast, "CANNOT START: %s", apps[idx].name);
+                                                launch_fail_toast(toast, sizeof toast, apps[idx].name);
                                                 toast_ms = TOAST_MS;
                                             }
                                         }