docker: track cadgenbench @main instead of a pinned SHA

Dockerfile

@@ -37,9 +37,11 @@ COPY requirements.txt /tmp/requirements.txt
 RUN pip install --no-cache-dir -r /tmp/requirements.txt \
     && rm /tmp/requirements.txt
 
-# cadgenbench from the Public GitHub repo, pinned to a commit. Bumping
-# CADGENBENCH_SHA is the one-line path to picking up a new cadgenbench.
-ARG CADGENBENCH_SHA=b22a53c
+# cadgenbench from the Public GitHub repo. Defaults to `main` so every
+# image rebuild picks up the latest code (pre-v1: always-updated). Lock
+# to a specific commit SHA at the v1 release so published scores are
+# reproducible (see space-setup/post-gt-swap.md Stage F).
+ARG CADGENBENCH_SHA=main
 RUN pip install --no-cache-dir \
         "cadgenbench @ git+https://github.com/huggingface/cadgenbench.git@${CADGENBENCH_SHA}"