feat(docker): configure static git identity

docker/server.Dockerfile

@@ -25,6 +25,8 @@ RUN npm ci \
 FROM node:22-bookworm-slim
 
 ARG CODEMAN_RUNTIME_USER=codeman
+ARG GIT_USER_EMAIL=
+ARG GIT_USER_NAME=
 ARG PUID=1000
 ARG PGID=1000
 
@@ -48,6 +50,18 @@ RUN apt-get update \
       tmux \
  && rm -rf /var/lib/apt/lists/*
 
+# A runtime home is normally a bind mount, so user-level Git configuration is
+# not durable across a fresh deployment. Keep the operator-supplied identity in
+# the image's system config instead. Both values are required together to avoid
+# producing commits with a misleading partial identity.
+RUN set -eux; \
+    if [ -n "${GIT_USER_NAME}" ] || [ -n "${GIT_USER_EMAIL}" ]; then \
+      test -n "${GIT_USER_NAME}"; \
+      test -n "${GIT_USER_EMAIL}"; \
+      git config --system user.name "${GIT_USER_NAME}"; \
+      git config --system user.email "${GIT_USER_EMAIL}"; \
+    fi
+
 # The Docker CLI, taken from the official image rather than Debian's `docker.io`.
 # That package is the full ENGINE: with --no-install-recommends it still pulls 15
 # packages including containerd, runc, dmsetup and iptables, none of which a