feat: M6.40批 — 阅读器UI改版(书架list·grid+空态骨架+界面设置+App设置页+header·footer+背景黑默认) + 系统级音量翻页映射 + P1 MD3(select面板28/对话框按钮胶囊) + MeowPanel写端点护栏 + SDK公开仓·文档同步

- reader: app.c/shelf.c/reader.c 全套UI; 新增 reader_conf(reader.conf)/settings(App设置页)/reader_ipc(音量翻页IPC响应); app.json加volume_page
- launcher: keys.c meow_volpage_*门 + util.c app_id→fd映射(HELLO记fd/断开清) + app_launcher.c 前台三处接线(进入sink/按键路径volpage_key/离开clear) → 前台声明volume_page的App音量键→MSG_KEY_PAGEUP/PAGEDOWN翻页(非阅读器前台音量照旧)
- sdk: meow_select.c 底部面板28 + meow_ui_dialog.c 对话框按钮胶囊(h/2) + test_meow_ui_select.c修采样
- meowpanel: /api/net/policy·/api/power/policy 加防自锁+policy默认关两条护栏(panel.policy_enabled默认0)
- 文档: MEOW_APP_SDK.md §12.6 + meowpanel README端点表

0warning;宿主测试全过;二进制留批量批次未入库

patch_v2/meowpanel/src/mp_store.c

@@ -69,6 +69,10 @@ static const setdef_t g_sets[] = {
     { "panel.pin",                  ST_STR,  "",     0,0, NULL, NULL, "面板" },
     { "panel.auth_enabled",         ST_BOOL, "0",    0,0, NULL, NULL, "面板" },
     { "panel.auth_pass",            ST_STR,  "",     0,0, NULL, NULL, "面板" },
+    /* panel.policy_enabled — 策略写「默认关」门禁（guard③）：POST /api/net/policy 与 /api/power/policy
+     * 默认关闭（缺省 0），置 1 才放行。落 settings.conf（「面板」组，前端设置页可开启），仅作面板侧门禁记录，
+     * 不影响 powermgr 的 `enacted`（那是服务端「策略是否已应用」，二者独立）。 */
+    { "panel.policy_enabled",       ST_BOOL, "0",    0,0, NULL, NULL, "面板" },
 };
 #define SETS_COUNT ((int)(sizeof g_sets / sizeof g_sets[0]))
 
@@ -143,6 +147,11 @@ int settings_get_int(const char *key, int defv)
     return r;
 }
 
+int panel_policy_write_enabled(void)
+{
+    return settings_get_int("panel.policy_enabled", 0) ? 1 : 0;
+}
+
 int brightness_clamp(int v)
 {
     int mn = settings_get_int("display.brightness_min", 1);