feat: 链路控制、延迟校准与长测工具，补全文档

- 固件：新增 link_control / stream_control，覆盖运行中 Wi-Fi 断线恢复、取帧节拍、
  温控与质量/帧率减载；UDP 发送增加有界重试预算与帧期限，PSRAM JPEG 直发减少拷贝。
- 协议：重组器严格校验分片布局，统计未收齐、超时与完全缺失的帧，处理帧号回绕与设备重启。
- 桌面端：视频改 latest-value 通道并前置帧时间标记，拒绝积压和慢解码的过期画面；新增
  延迟标记页与 --latency-report 校准，完善录制、服务端与退出流程。
- 文档与脚本：新增硬件、开发、延迟、功耗、实时性、稳定性文档和改动记录，重写根 README；
  新增构建、性能、延迟与串口长测脚本，以及长测客户端脚本。
- 构建：固定 esp-1.97.0.0 工具链，分区表随构建复制，更新 sdkconfig 与忽略规则。

desktop/src-tauri/src/state.rs

@@ -24,14 +24,14 @@ use cam_core::armor::{ArmorHealthStore, HealthTracker};
 use cam_core::config::{Config, Role};
 use cam_core::password;
 use cam_core::receiver::{Discovery, LatestFrames, Receiver};
-use cam_core::ArmorSource;
 use cam_core::slots::SlotAllocator;
 use cam_core::snapshot::{
-    resolve_outcomes, ArmorBoardDto, CameraDto, CameraStatsDto, ConfigView, HitDto, Snapshot,
-    SlotsDto, TeamHealthDto,
+    resolve_outcomes, ArmorBoardDto, CameraDto, CameraStatsDto, ConfigView, HitDto, SlotsDto,
+    Snapshot, TeamHealthDto,
 };
 use cam_core::stats::{FpsWindow, DEFAULT_WINDOW};
-use tokio::sync::broadcast;
+use cam_core::ArmorSource;
+use tokio::sync::{broadcast, watch};
 
 use crate::recording::{now_ms, RecordingSet};
 use crate::server::{self, ServerMsg, WireMsg};
@@ -67,6 +67,7 @@ pub struct AppState {
     pub recordings: Arc<RecordingSet>,
 
     tx: broadcast::Sender<Arc<ServerMsg>>,
+    video: server::VideoSender,
     /// 回环上已经绑好的 WebSocket listener，等 `spawn_background` 取走。
     ///
     /// 先绑再交给后台任务，是为了让"端口绑不上"在启动阶段就报错，而不是变成一个永远
@@ -92,38 +93,43 @@ impl AppState {
         config: Config,
         mut notes: Vec<String>,
         demo: bool,
-    ) -> Result<(Arc<Self>, Option<std::net::UdpSocket>, Option<std::net::UdpSocket>)> {
+    ) -> Result<(
+        Arc<Self>,
+        Option<std::net::UdpSocket>,
+        Option<std::net::UdpSocket>,
+    )> {
         let role = config.role;
-        let bound = if role == Role::Team { config.camera_id } else { None };
+        let bound = if role == Role::Team {
+            config.camera_id
+        } else {
+            None
+        };
 
         // 视频端口绑不上**不**致命：界面照常起来，并把原因写在最显眼的地方。
         //
         // 一开始这里是 `?`（直接退出）。但那样一来，现场看到的是一次闪退加上一句只出现
         // 在 stderr 的话——从访达双击启动时连 stderr 都没有。让窗口起来并说明原因，比
         // 静默退出有用得多；而且"另一个客户端已经在跑"恰好是最常见的原因。
-        let (receiver, video_socket) = match Receiver::start(
-            protocol::BROADCAST_ADDR,
-            role.to_protocol(),
-            bound,
-        ) {
-            Ok((receiver, socket)) => (Arc::new(receiver), Some(socket)),
-            Err(err) => {
-                log::error!("could not bind UDP {}: {err}", protocol::DEFAULT_PORT);
-                notes.push(format!(
-                    "绑不上 UDP {}：{err}。多半是同一个端口上已经跑着另一个客户端 \
+        let (receiver, video_socket) =
+            match Receiver::start(protocol::BROADCAST_ADDR, role.to_protocol(), bound) {
+                Ok((receiver, socket)) => (Arc::new(receiver), Some(socket)),
+                Err(err) => {
+                    log::error!("could not bind UDP {}: {err}", protocol::DEFAULT_PORT);
+                    notes.push(format!(
+                        "绑不上 UDP {}：{err}。多半是同一个端口上已经跑着另一个客户端 \
                      （旧的 Slint 版或另一份本程序）。画面收不到，其它功能照常。",
-                    protocol::DEFAULT_PORT
-                ));
-                (
-                    Arc::new(Receiver::new(
-                        protocol::BROADCAST_ADDR,
-                        role.to_protocol(),
-                        bound,
-                    )),
-                    None,
-                )
-            }
-        };
+                        protocol::DEFAULT_PORT
+                    ));
+                    (
+                        Arc::new(Receiver::new(
+                            protocol::BROADCAST_ADDR,
+                            role.to_protocol(),
+                            bound,
+                        )),
+                        None,
+                    )
+                }
+            };
 
         let discovery = receiver.discovery();
         let latest = receiver.latest_frames();
@@ -141,6 +147,7 @@ impl AppState {
         };
 
         let (tx, _) = broadcast::channel(server::CHANNEL_CAPACITY);
+        let (video, _) = watch::channel(server::VideoFrames::new());
         let (listener, port) = tauri::async_runtime::block_on(server::bind())
             .context("绑不上本地 WebSocket 端口（回环地址）")?;
 
@@ -157,6 +164,7 @@ impl AppState {
             slots: Mutex::new(SlotAllocator::new()),
             recordings: RecordingSet::new(),
             tx,
+            video,
             listener: Mutex::new(Some(listener)),
             port,
             token: server::random_token(),
@@ -175,15 +183,14 @@ impl AppState {
     ///
     /// 必须在 `Arc<AppState>` 建好之后调用（sink 里要持有 state 的通道）。
     pub fn install_sinks(self: &Arc<Self>) {
-        let tx = self.tx.clone();
+        let video = self.video.clone();
         let recordings = Arc::clone(&self.recordings);
 
         // 帧的 sink：在接收线程里跑，只做"编码一次 + 广播"。这一份字节所有界面共用。
         self.receiver
             .set_frame_sink(Arc::new(move |frame: Arc<protocol::Frame>| {
                 recordings.feed(&frame);
-                let bytes = server::encode_frame(&frame);
-                let _ = tx.send(Arc::new(ServerMsg::Binary(bytes.into())));
+                server::publish_video(&video, &frame);
             }));
 
         let tx = self.tx.clone();
@@ -240,9 +247,10 @@ impl AppState {
         let token = self.token.clone();
         let tx = self.tx.clone();
         let clients = Arc::clone(&self.clients);
+        let video = self.video.clone();
 
         tauri::async_runtime::spawn(async move {
-            server::serve(listener, token, tx, clients).await;
+            server::serve(listener, token, tx, video, clients).await;
         });
 
         let state_for_loop = Arc::clone(&state);
@@ -306,7 +314,9 @@ impl AppState {
         // 本来就要看到全场。
         let open = match role {
             Role::Referee => true,
-            Role::Team => self.discovery_open.load(Ordering::Relaxed) && self.unlocked.load(Ordering::Relaxed),
+            Role::Team => {
+                self.discovery_open.load(Ordering::Relaxed) && self.unlocked.load(Ordering::Relaxed)
+            }
         };
         self.receiver.set_discovery_all(open);
 
@@ -457,7 +467,12 @@ impl AppState {
 
     /// 推进帧率窗口与槽位分配。
     pub fn tick(&self) {
-        let online: Vec<u32> = self.discovery.online_cameras().iter().map(|c| c.id).collect();
+        let online: Vec<u32> = self
+            .discovery
+            .online_cameras()
+            .iter()
+            .map(|c| c.id)
+            .collect();
         let online_set: HashSet<u32> = online.iter().copied().collect();
 
         {
@@ -539,8 +554,12 @@ impl AppState {
             })
             .collect();
 
-        let armor_boards: Vec<ArmorBoardDto> =
-            self.armor.boards().iter().map(ArmorBoardDto::from).collect();
+        let armor_boards: Vec<ArmorBoardDto> = self
+            .armor
+            .boards()
+            .iter()
+            .map(ArmorBoardDto::from)
+            .collect();
 
         let slots = self.slots.lock().expect("slots mutex poisoned").slots();
 
@@ -627,7 +646,9 @@ impl AppState {
 
         if let Some(board) = board {
             return match self.armor.health_of_board(board) {
-                Some(hp) => TeamHealthDto::present(team, Some(board), [hp; 4], low, &config.team_names),
+                Some(hp) => {
+                    TeamHealthDto::present(team, Some(board), [hp; 4], low, &config.team_names)
+                }
                 None => TeamHealthDto::absent(team, Some(board), &config.team_names),
             };
         }