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。

sdkconfig.defaults

@@ -4,6 +4,8 @@ CONFIG_ESP_MAIN_TASK_STACK_SIZE=8192
 CONFIG_ESP_SYSTEM_EVENT_TASK_STACK_SIZE=4096
 CONFIG_FREERTOS_IDLE_TASK_STACKSIZE=4096
 CONFIG_PTHREAD_TASK_STACK_SIZE_DEFAULT=4096
+# A retry yields one tick; use 1 ms ticks for bounded UDP backpressure waits.
+CONFIG_FREERTOS_HZ=1000
 
 # Run the CPU at 240 MHz.
 #
@@ -39,7 +41,8 @@ CONFIG_ESP32S3_INSTRUCTION_CACHE_32KB=y
 # module's defective flash byte. That offset is written by scripts/flash.sh, not
 # fixed here; see partitions.csv for why it cannot be a constant.
 CONFIG_PARTITION_TABLE_CUSTOM=y
-CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="../../../../../../partitions.csv"
+# The build scripts copy this file into the generated CMake project.
+CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions.csv"
 CONFIG_PARTITION_TABLE_OFFSET=0x8000
 
 # Octal PSRAM is mandatory for the N16R8 module (R8 == 8 MB OPI PSRAM). The
@@ -63,6 +66,11 @@ CONFIG_SPIRAM_TRY_ALLOCATE_WIFI_LWIP=n
 
 CONFIG_ESP_WIFI_IRAM_OPT=y
 CONFIG_ESP_WIFI_RX_IRAM_OPT=y
+# Enough TX slots for a JPEG burst and multiple subscribers. JPEG data remains
+# in PSRAM; Wi-Fi DMA buffers stay in internal memory.
+CONFIG_ESP_WIFI_DYNAMIC_TX_BUFFER_NUM=64
+CONFIG_ESP_WIFI_TX_BA_WIN=32
+CONFIG_ESP_WIFI_AMPDU_TX_ENABLED=y
 
 # Socket buffers sized for a video frame rather than for a text request.
 #
@@ -77,11 +85,11 @@ CONFIG_CAMERA_TASK_STACK_SIZE=4096
 
 # Run the camera task on CPU1.
 #
-# The WiFi task is pinned to CPU0. esp32-camera's capture task spends its time
-# in short, latency-sensitive bursts (DMA completion, the JPEG marker search,
-# the copy into the frame buffer) and gets preempted on a shared core, which
-# lengthens every frame. On a two-core part there is no reason to share.
+# Explicitly select the choice: disabling CORE0 alone leaves Kconfig free to
+# select it again. CPU0/CPU1 A/B tests both reach the sensor's ~22 fps ceiling;
+# the observed transport bottleneck is not resolved by changing this affinity.
 CONFIG_CAMERA_CORE0=n
+CONFIG_CAMERA_CORE1=y
 
 # PSRAM DMA is left off deliberately.
 #
@@ -102,4 +110,4 @@ CONFIG_CAMERA_DMA_BUFFER_SIZE_MAX=32768
 # driver, and refuses to run both in one image. esp32-camera picks one of them
 # for the SCCB bus; whichever it picks, the other has to stay out of the image,
 # so the conflict check is skipped here.
-CONFIG_I2C_SKIP_LEGACY_CONFLICT_CHECK=y
+CONFIG_I2C_SKIP_LEGACY_CONFLICT_CHECK=y