ESP32-S3 摄像头图传：固件 + Slint 客户端 + 共享协议

两块 ESP32-S3-WROOM-1-N16R8 图传板（DVP 接口接 OV2640/OV3660/OV5640），
向队伍客户端与裁判终端推 UDP 图传。固件是跑在 ESP-IDF 上的 Rust，用官方
esp32-camera 组件采集；客户端是 Rust + Slint 桌面程序。

三个 crate 各自独立构建：
  .            firmware，交叉编译到 Xtensa
  protocol/    线路格式与帧重组，两端共用，无 ESP-IDF 依赖，有单元测试
  client/      Slint 桌面客户端

视频走 UDP 而非 TCP：实测传感器产出 22 fps，TCP MJPEG 只送出 1.9 fps，
且只占用链路能力的 1%——链路是空的，帧堵在队头阻塞后面等一个实时画面
等不起的重传计时器。改为独立数据报、不重传、缺片丢整帧后达到 20.8 fps。

发现是双向的：板子每 2 秒广播 Hello，客户端广播 Subscribe，板子据此定向
推流。板子身份由 MAC 派生，重启不变，所以客户端可以把绑定存进配置。

裁判端同时收两块板子（每个发送方一个重组器），队伍端绑定其中一块并只显示
自己那一边的血量。装甲板接口已预留（ArmorSource trait + ARMOR_PORT），
当前无数据源，界面显示占位符。

vendor 了 esp32-camera 2.1.7：组件注册表的版本求解器找不到它，且需要打一处
补丁（见 components/esp32-camera/target/esp32s3/ll_cam.c）。

.gitignore 三条 target/ 都锚定在根目录，因为 protocol/ 与 client/ 各自也是
独立 crate；而 components/esp32-camera/target/ 是上游的按芯片分目录，里面是
源码，必须保留。

Cargo.toml

@@ -0,0 +1,45 @@
+[package]
+name = "esp32"
+version = "0.1.0"
+edition = "2021"
+resolver = "2"
+rust-version = "1.82"
+
+[[bin]]
+name = "esp32"
+harness = false # no built-in test harness, keeps the generated project simple
+
+[dependencies]
+log = "0.4"
+anyhow = "1"
+embedded-svc = "0.29"
+esp-idf-svc = "0.53"
+
+# The UDP wire format, shared with the desktop client in client/. It is built for
+# the host too (see protocol/.cargo/config.toml), which is what lets the protocol
+# have unit tests: the frame assembler and the encoder are the parts most likely to
+# be subtly wrong, and neither can be exercised from the firmware.
+protocol = { path = "protocol" }
+
+[build-dependencies]
+embuild = "0.33.5"
+
+# The official `esp32-camera` component is not part of ESP-IDF itself. It is
+# vendored under components/esp32-camera so the build does not depend on the
+# component registry, and so that one IDF v6 incompatibility can be patched -
+# see the "LOCAL PATCH" comment in components/esp32-camera/target/esp32s3/ll_cam.c.
+#
+# `cam_wrapper` is a tiny local component (see components/cam_wrapper) that
+# wraps `camera_config_t` in a union-free plain struct, which makes the Rust
+# side safe to construct.
+[[package.metadata.esp-idf-sys.extra_components]]
+component_dirs = ["components/esp32-camera", "components/cam_wrapper"]
+bindings_header = "bindings.h"
+bindings_module = "camera"
+
+[profile.release]
+opt-level = "s"
+
+[profile.dev]
+debug = true
+opt-level = "z"