remove detection from the node

dora-zed publishes camera data only. The two engines under src/engines/, the
objects output, the ZED_ENGINE/ZED_DETECTION_*/ZED_ONNX_* variables and the
ZED_PC_MODE=ROI crop are gone, along with the standalone engine test and the
model export script.

This drops the unconditional ONNX Runtime requirement from CMakeLists, the
Dockerfile and the install scripts, so the node now configures on a machine
with no ONNX Runtime — which is what blocked the Jetson build, since there is
no official ARM64 GPU binary.

zed_native is dropped rather than kept: it is bound to the live camera handle
and cannot run in a node that receives images over a dataflow. The removed
code remains reachable at tag v0.1.0.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y7g2cBJ5e3r15ZbJ9WZn8c

scripts/install_linux_arm.sh

@@ -9,11 +9,6 @@
 #   JetPack 6.2.2   (L4T 36.5)
 #   JetPack 7.0     (L4T 38.2) — Jetson Thor
 #   JetPack 7.1     (L4T 38.4)
-#
-# ONNX Runtime: Microsoft does not publish official GPU binaries for ARM64.
-#   ONNX Runtime is still needed to configure the build; only the yolo_onnx
-#   engine uses it at runtime. Build it from source:
-#   https://onnxruntime.ai/docs/build/eps.html#tensorrt
 set -euo pipefail
 
 ZED_VERSION="5.2"
@@ -63,13 +58,5 @@ else
     sudo "${TMP_DIR}/ZED_SDK.run" -- silent skip_python skip_tools
 fi
 
-# --- ONNX Runtime ---
-echo ""
-echo ">>> ONNX Runtime (ARM64 GPU): no official pre-built binary available."
-echo "    Needed to configure the build; only yolo_onnx uses it at runtime."
-echo "    Build from source:"
-echo "      https://onnxruntime.ai/docs/build/eps.html#tensorrt"
-echo ""
-
-echo ">>> Done. You can now run: mkdir -p build && cd build && cmake .. && make install"
+echo ">>> Done. You can now run: scripts/build.sh"
 echo ">>> Downloaded files are in ${TMP_DIR}"