chore: 框架科学优化前的完整基线

在开始'设备契约层 + 目录重构 + 通止规装配'改造之前，先钉住当前可运行状态，
使后续任何删除/重构都可回退。

本基线包含：
- 现有 ROS 2 工作区全部源码（arm_application / arm_control / arm_bringup 等）
- 官方 flexiv_ros2 栈（含 flexiv_hardware / flexiv_controllers 等符号链接）
- 设备契约层 src/arm_interfaces（新增，46 项单测通过）
- devices/ 设备选型与品牌清单（新增）
- scripts/gen_site_example.py 与由它生成的 config/site.example.yaml

按 .gitignore 排除：build/ / install/ / log/ / config/site.yaml / 模型权重二进制。

scripts/fetch_isaac_flexiv.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+# Clone Flexiv Isaac Sim integration repos into thirdparty/
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+TP="${ROOT}/thirdparty"
+mkdir -p "${TP}"
+cd "${TP}"
+
+clone_or_update() {
+  local url="$1"
+  local dir="$2"
+  if [[ -d "${dir}/.git" ]]; then
+    echo "Updating ${dir}..."
+    git -C "${dir}" pull --ff-only || true
+  else
+    echo "Cloning ${dir}..."
+    git clone --depth 1 "${url}" "${dir}"
+  fi
+}
+
+clone_or_update https://github.com/flexivrobotics/flexiv_sim_plugin.git flexiv_sim_plugin
+clone_or_update https://github.com/flexivrobotics/isaac_sim_ws.git isaac_sim_ws
+clone_or_update https://github.com/flexivrobotics/flexiv_description.git flexiv_description
+
+# Optional: RDK sources next to sim (if not already under src/)
+if [[ ! -d "${ROOT}/src/flexiv_rdk" ]]; then
+  clone_or_update https://github.com/flexivrobotics/flexiv_rdk.git flexiv_rdk
+fi
+
+cat <<EOF
+
+Isaac / description repos are under: ${TP}
+
+Next (Isaac path):
+  1) Install NVIDIA Isaac Sim
+  2) Follow flexiv_sim_plugin README (Elements Studio → External / Isaac)
+  3) cd ${TP}/isaac_sim_ws && bash install_ws.sh <isaac_sim_root>
+  4) Configure robot instance for Rizon4-063989 in app_config.yaml
+  5) Primitive docs: https://primitive.flexiv.cn/primitives/zh-CN/3.10/rizon4/index.html
+  6) RDK manual (CN): https://flexiv.cn/software/rdk/manual/index.html
+
+ROS 2 path (separate):
+  ${ROOT}/scripts/fetch_flexiv.sh
+
+EOF