huskies: merge 1107 story Chat bootstrap Phase 2a: stack-overlay framework + Rust and Node stack overlays

docker/stacks/rust/Dockerfile.fragment

@@ -0,0 +1,37 @@
+# Rust stack overlay fragment.
+#
+# Layer this on top of huskies-project-base to produce a project container
+# with a full Rust toolchain, rust-analyzer, and cargo-nextest.
+#
+# Build the combined image:
+#   (echo "FROM huskies-project-base"; \
+#    cat docker/stacks/rust/Dockerfile.fragment) | \
+#   docker build -t huskies-project-rust -
+#
+# Adding a new stack: create docker/stacks/<name>/Dockerfile.fragment and
+# docker/stacks/<name>/markers — no changes to orchestration code required.
+
+USER root
+
+# Build tools required by rustup and many Rust crates.
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        build-essential \
+        pkg-config \
+        libssl-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+ENV RUSTUP_HOME="/home/huskies/.rustup" \
+    CARGO_HOME="/home/huskies/.cargo"
+
+# Install stable Rust + rust-analyzer component as the huskies user.
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+        | su huskies -c "sh -s -- -y --no-modify-path --default-toolchain stable" \
+    && /home/huskies/.cargo/bin/rustup component add rust-analyzer \
+    && chown -R huskies:huskies /home/huskies/.rustup /home/huskies/.cargo
+
+# cargo-nextest: fast Rust test runner used by huskies quality gates.
+RUN curl -LsSf https://get.nexte.st/latest/linux | tar zxf - -C /usr/local/bin
+
+ENV PATH="/home/huskies/.cargo/bin:${PATH}"
+
+USER huskies