Let the page ask the radio whether it sees an installed app

GET /api/apps/radio opens the firmware's serial port and sends 0x0730 for all sixteen slots, so the answer comes from the running firmware rather than from our reading of the file -- which is the check that matters, because the bytes can be right and the firmware still refuse a slot. Measured through the page after installing Beam.app into slot 0: slot 0 -> Beam 1.0, 1100 B, crc 0xd976058, shortcut beam, committed; slots 1..3 -> status 2 with unrelated data, the resource-block overlap the install guard refuses. A button beside the table asks it and shows the answer in its own column.

The server gives its own emulator a serial port (--serial-port, default 4445) and uvk5_slots_serial.Radio gained a public app_info(slot), so nothing reaches into a private helper. uvk5_apps.parse_radio_reply decodes the answer and is tested without a radio. Also recorded: QEMU needs the mingw64 DLLs on PATH, and started by hand without them it exits before opening QMP, which surfaces only as 'QMP socket never appeared'.

README.zh-CN.md

@@ -302,6 +302,7 @@ uvk5_elf.sh            探针脚本从哪里找固件（环境变量，然后本
 | `GET /api/apps` | 同一 flash 镜像里 Labs 版的叠加应用槽 |
 | `POST /api/apps/<n>` | 请求体是一个 `.app`；装进应用槽 `n`（加 `?force=1` 可覆盖非应用数据） |
 | `POST /api/apps/<n>/erase` | 清空应用槽 `n` |
+| `GET /api/apps/radio` | 问正在运行的固件它在每个应用槽里看到了什么（`0x0730`） |
 | `POST /api/flash` | 请求体是一份 flash 镜像；之后就用它 |
 
 画面现在取自显示控制器自己的内存：对面板的 `gram` 属性做一次 QMP `qom-get`。