fix(docker): make release image a usable dev environment

Replace the multi-stage build-artifacts-only image with a single-stage
development image that has gcc, clang, cmake, gdb, and the Universal
headers installed to /usr/local. Users can write, compile, and run C++
programs using Universal directly inside the container.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Ravenwater

.github/workflows/release.yml

@@ -120,7 +120,6 @@ jobs:
         with:
           context: .
           file: docker/Dockerfile.release
-          target: release
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}

README.md

@@ -121,15 +121,21 @@ A quick description of the structure of the number system parameterization can b
 
 ## Quick start
 
-If you just want to experiment with the number system tools and test suites and don't want to bother cloning and building the source code, there is a Docker container to get started:
+If you just want to experiment with Universal without cloning and building the source code, there is a Docker container with compilers, cmake, and the library pre-installed:
 
 ```text
 > docker pull stillwater/universal
 > docker run -it --rm stillwater/universal bash
-stillwater@b3e6708fd732:~/universal/build$ ls
-CMakeCache.txt       Makefile      cmake-uninstall.cmake  playground  universal-config-version.cmake
-CMakeFiles           applications  cmake_install.cmake    tests       universal-config.cmake
-CTestTestfile.cmake  c_api         education              tools       universal-targets.cmake
+stillwater@container:~$ ieee 1.5
+stillwater@container:~$ cat > hello.cpp << 'EOF'
+#include <universal/number/posit/posit.hpp>
+#include <iostream>
+int main() {
+    sw::universal::posit<16,2> p = 1.5;
+    std::cout << p << '\n';
+}
+EOF
+stillwater@container:~$ g++ -std=c++20 -I/usr/local/include/sw -o hello hello.cpp && ./hello
 ```
 
 [Here](docs/command-line-tools.md) is a quick reference of what the command line tools have to offer.

docker/Dockerfile.release

@@ -1,59 +1,48 @@
-# Self-contained multi-stage release Dockerfile for Universal Numbers Library.
-# No dependency on pre-built stillwater/builders:* images.
+# Universal Numbers Library — development image for Docker Hub.
+#
+# Provides a ready-to-use C++ development environment with the Universal
+# library installed, compilers, cmake, and command-line inspection tools.
 #
 # Usage:
-#   docker build --target release -t stillwater/universal:latest -f docker/Dockerfile.release .
-#   docker run --rm stillwater/universal:latest ieee 1.5
-
-ARG BUILD_TARGET=UNIVERSAL_BUILD_ALL
-
-# ---------------------------------------------------------------------------
-# Builder stage
-# ---------------------------------------------------------------------------
-FROM ubuntu:24.04 AS builder
+#   docker build -t stillwater/universal:latest -f docker/Dockerfile.release .
+#   docker run -it --rm stillwater/universal bash
+#
+# Then inside the container:
+#   cat > hello.cpp << 'EOF'
+#   #include <universal/number/posit/posit.hpp>
+#   #include <iostream>
+#   int main() {
+#       sw::universal::posit<16,2> p = 1.5;
+#       std::cout << p << '\n';
+#   }
+#   EOF
+#   g++ -std=c++20 -I/usr/local/include/sw -o hello hello.cpp && ./hello
+
+FROM ubuntu:24.04
 
 RUN apt-get update \
  && apt-get install -y --no-install-recommends \
         build-essential \
+        clang \
         cmake \
         ninja-build \
+        gdb \
+        git \
         ca-certificates \
  && apt-get clean && rm -rf /var/lib/apt/lists/*
 
-RUN useradd -ms /bin/bash stillwater
-USER stillwater
-
-COPY --chown=stillwater:stillwater . /home/stillwater/universal
-WORKDIR /home/stillwater/universal
-
-ARG BUILD_TARGET
-RUN cmake -B build -G Ninja \
+# Copy source, build command-line tools, install headers + tools to /usr/local
+COPY . /tmp/universal-src
+RUN cmake -S /tmp/universal-src -B /tmp/universal-build -G Ninja \
         -DCMAKE_BUILD_TYPE=Release \
-        -D${BUILD_TARGET}=ON \
-        -DUNIVERSAL_BUILD_CMD_LINE_TOOLS=ON \
-        -DUNIVERSAL_BUILD_DEMONSTRATION=OFF \
- && cmake --build build -j$(nproc)
-
-# ---------------------------------------------------------------------------
-# Release stage — minimal image with pre-built binaries
-# ---------------------------------------------------------------------------
-FROM ubuntu:24.04 AS release
+        -DUNIVERSAL_BUILD_TOOLS_CMD_LINE=ON \
+ && cmake --build /tmp/universal-build -j$(nproc) \
+ && cmake --install /tmp/universal-build --prefix /usr/local \
+ && rm -rf /tmp/universal-src /tmp/universal-build
 
 RUN useradd -ms /bin/bash stillwater
 USER stillwater
-
-COPY --from=builder /usr/bin/cmake  /usr/local/bin/
-COPY --from=builder /usr/bin/ctest  /usr/local/bin/
-COPY --from=builder /home/stillwater/universal/*.md /home/stillwater/universal/
-COPY --chown=stillwater:stillwater --from=builder \
-        /home/stillwater/universal/docs /home/stillwater/universal/docs
-COPY --chown=stillwater:stillwater --from=builder \
-        /home/stillwater/universal/build /home/stillwater/universal/build
-
-# Expose command-line tools on PATH
-COPY --from=builder /home/stillwater/universal/build/tools/cmd/* /usr/local/bin/
-
-WORKDIR /home/stillwater/universal/build
+WORKDIR /home/stillwater
 
 ENV CONTAINER_ID="Universal Number Systems Container"
 CMD ["/usr/bin/env", "bash"]

docker/build-release.sh

@@ -18,7 +18,6 @@ VERSION=$(git -C "$ROOT_DIR" describe --tags --abbrev=0 2>/dev/null || \
 echo "Building $REPO:$VERSION"
 
 docker build \
-    --target release \
     -t "$REPO:$VERSION" \
     -t "$REPO:latest" \
     -f "$SCRIPT_DIR/Dockerfile.release" \

docs-site/src/content/docs/getting-started/docker.md

@@ -5,20 +5,27 @@ sidebar:
   order: 2
 ---
 
-If you want to experiment with Universal's number system tools and test suites without cloning and building the source code, use the Docker container:
+The Docker image provides a ready-to-use C++ development environment with compilers, cmake, the Universal library headers pre-installed, and command-line inspection tools on the PATH.
 
 ```bash
 docker pull stillwater/universal
 docker run -it --rm stillwater/universal bash
 ```
 
-Once inside the container, all tools and test executables are pre-built and ready to use:
+Write and compile programs using Universal directly inside the container:
 
-```text
-stillwater@b3e6708fd732:~/universal/build$ ls
-CMakeCache.txt       Makefile      cmake-uninstall.cmake  playground  universal-config-version.cmake
-CMakeFiles           applications  cmake_install.cmake    tests       universal-config.cmake
-CTestTestfile.cmake  c_api         education              tools       universal-targets.cmake
+```cpp
+// hello.cpp
+#include <universal/number/posit/posit.hpp>
+#include <iostream>
+int main() {
+    sw::universal::posit<16,2> p = 1.5;
+    std::cout << p << '\n';
+}
+```
+
+```bash
+g++ -std=c++20 -I/usr/local/include/sw -o hello hello.cpp && ./hello
 ```
 
 ## Try the Command-Line Tools