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/list_realsense.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# List plugged RealSense cameras (serials used in site.yaml).
+set -eo pipefail
+python3 - <<'PY'
+import pyrealsense2 as rs
+known = {
+    "352122274408": "left wrist D405 (arm 89, parallel gripper)",
+    "260522274442": "right wrist D405 (arm 91, rotary gripper)",
+    "262522073161": "overhead D435 (between arms, eye-to-hand)",
+}
+ds = list(rs.context().devices)
+print(f"n={len(ds)}")
+for d in ds:
+    sn = d.get_info(rs.camera_info.serial_number)
+    name = d.get_info(rs.camera_info.name)
+    usb = d.get_info(rs.camera_info.usb_type_descriptor)
+    fw = d.get_info(rs.camera_info.firmware_version)
+    role = known.get(sn, "(unassigned — add to site.yaml cameras:)")
+    print(f"  {name:22} serial={sn} USB={usb} fw={fw}")
+    print(f"    -> {role}")
+PY