add a container build environment

Dockerfile provisions CUDA 12.8, ZED SDK 5.2, ONNX Runtime and Rust on
Ubuntu 24.04, the newest release Stereolabs ships a ZED SDK for, so the
node can be compiled and the build verified without installing the SDK
stack on the host.

The compile needs --gpus all: libsl_zed.so links against the CUDA driver
API, NVDEC and NVENC, which ship with the display driver rather than the
CUDA toolkit and so exist in no image. The container runtime mounts them
from the host, and only includes NVDEC/NVENC when the video capability
is requested.

Runs as the invoking user so build/ and bin/ are not left root-owned,
which needs the toolchain outside /root and the ZED SDK directory
readable to an arbitrary uid.

AGENTS.md

@@ -18,6 +18,8 @@ The binary is installed to `bin/dora_zed` relative to the repo root.
 
 The first build clones dora-rs from GitHub and compiles `dora-node-api-cxx` via Cargo. This takes a while. Subsequent builds are incremental. If `DORA_ROOT_DIR` is set to a local dora checkout, it builds against that instead.
 
+For a build without installing the SDK stack on the host, see the `Dockerfile` (Ubuntu 24.04 — the newest release with a ZED SDK; there is no Stereolabs build for 26.04). Run the compile with `--gpus all`.
+
 ## Run
 
 ```bash
@@ -39,6 +41,7 @@ Camera and detection behavior is configured entirely through environment variabl
 - **`src/main.cc`** — Dora event loop. Selects engine via `ZED_ENGINE` env var (`yolo_onnx`/`onnx` or `native`), holds a `std::unique_ptr<engines::Engine>`. Parses `ZED_PC_MODE` (`FULL`/`HALF`/`ROI`) once before the loop. On any input event (intended to be driven by a tick timer; the id is not inspected): calls `camera.grab()` and `detector->detect()`, then sends `image_bgr`, `point_cloud`, `camera_info`, and `objects` outputs. Point cloud output varies by mode: `FULL` sends the raw `sl::Mat` pointer (no copy); `HALF` downsamples by 2 in each dimension; `ROI` emits only valid points within detected bounding boxes as a flat `[N, 4]` array. Handles reconnection on grab failure.
 - **`DoraTargets.cmake`** — Handles building or fetching dora-rs and generating the CXX bridge files. Two paths: local (`DORA_ROOT_DIR`) or git clone. Produces `dora_node_api_cxx` library and the `node_bridge.cc` glue.
 - **`dataflow.yml`** — Example dora dataflow definition using the `git:` source format.
+- **`Dockerfile`** — Ubuntu 24.04 x86-64 build environment (CUDA 12.8, ZED SDK 5.2, ONNX Runtime, Rust). No ARM64/Jetson image; build natively there. No camera needed; run the compile with `--gpus all`. Sets `NVIDIA_DRIVER_CAPABILITIES=compute,utility,video` — the `video` capability is what makes the container runtime mount NVDEC/NVENC, which `libsl_zed.so` links against. ONNX Runtime's CMake package files are relocated to `/usr/local/lib/cmake` because Ubuntu's multiarch CMake does not search `lib64`. Rust lives at `/usr/local/{rustup,cargo}` rather than `/root` so the build can run as the invoking user. `docker build -t dora-zed-build . && docker run --rm --gpus all --user "$(id -u):$(id -g)" -v "$PWD:/src" -v dora-zed-cargo:/usr/local/cargo/registry dora-zed-build`.
 - **`scripts/export_yolo.py`** — PEP 723 uv script. Exports a standard YOLOv11 model to ONNX for closed-vocabulary detection. Run: `uv run scripts/export_yolo.py --model n --output-dir models/`.
 - **`src/test_yolo_onnx.cc`** — Standalone C++ test binary (`bin/test_yolo_onnx`). Exercises `YoloOnnx` with an image (default `test/assets/yolo.png`). No dora and no live camera required. Uses the same env vars as the main binary. Saves an annotated result image alongside the input.