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。

.cargo/config.toml

@@ -12,14 +12,7 @@ build-std = ["std", "panic_abort"]
 [env]
 MCU = "esp32s3"
 
-# Use the ESP-IDF installation and toolchains that are already on the machine
-# (eim's install under ~/.espressif) instead of downloading another copy into
-# ./.embuild. Without this the first build re-downloads several hundred MB of
-# Xtensa GCC/LLVM.
-#
-# `global` means ~/.espressif, which is where eim installs.
-#
-# Drop these two lines to let esp-idf-sys clone and fetch the ESP-IDF version it
-# pins itself (v5.5.5 by default), into ~/.espressif.
-IDF_PATH = { value = "/Users/peng/.espressif/esp-idf/v5.5.5", force = true }
-ESP_IDF_TOOLS_INSTALL_DIR = { value = "global", force = true }
+# esp-idf-sys downloads this version unless IDF_PATH points to an existing SDK.
+# Keep machine-specific paths in the environment instead of this shared file.
+ESP_IDF_VERSION = { value = "v5.5.5", force = false }
+ESP_IDF_TOOLS_INSTALL_DIR = { value = "global", force = false }