Assisted-by: GLM-5.3 via pi

diff --git a/.ramekin/Dockerfile b/.ramekin/Dockerfile
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+FROM ramekin-agent
+
+# Rust toolchain for parallax. Edition 2024 needs a recent stable, so use
+# rustup rather than Debian's rustc.
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+    | sh -s -- -y --default-toolchain stable --profile minimal \
+    && /root/.cargo/bin/rustup component add clippy rustfmt llvm-tools
+
+ENV PATH="/root/.cargo/bin:$PATH"