Assisted-by: Claude Opus 5.5 via Claude Code

diff --git a/.ramekin/Dockerfile b/.ramekin/Dockerfile
index ec5be30..973897c 100644
--- a/.ramekin/Dockerfile
+++ b/.ramekin/Dockerfile
@@ -3,5 +3,12 @@ FROM ramekin-agent
 RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain stable --profile minimal
 ENV PATH="/root/.cargo/bin:${PATH}"
 
-# The minimal profile omits these; `just` runs both.
-RUN rustup component add rustfmt clippy
+# The minimal profile omits these; `just` runs all three (llvm-tools for
+# coverage).
+RUN rustup component add rustfmt clippy llvm-tools
+
+# bin/coverage reads profiles with grcov; same version as CI, built for
+# this machine's architecture.
+RUN curl --proto '=https' --tlsv1.2 -sSfL \
+        "https://github.com/marco-c/grcov/releases/download/v0.10.7/grcov-$(uname -m)-unknown-linux-gnu.tar.bz2" \
+    | tar xj -C /usr/local/bin