Commits of agents carry a co-author trailer naming the model

A git wrapper (docker/git-coauthor -> /usr/local/lib/codecraft/bin/git) adds
--trailer "$CODECRAFT_COMMIT_TRAILER" right after the commit subcommand; the
agent shell puts it first on PATH and sets the trailer in the script itself
(works inside the sandbox, which clears the environment). Default text:
"Co-Authored-By: {model} ({provider}) via CodeCraft" (server.commit_trailer,
Settings -> General; empty = off). Git skips duplicates (amend, model wrote it).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Dockerfile

@@ -96,6 +96,8 @@ COPY --from=cli /out /app/cli
 # Used with a mounted /var/run/docker.sock (see docs/MOVING.md, --docker-sock).
 COPY --from=dockercli /docker /usr/local/bin/docker
 COPY server/ghidra /app/ghidra
+# git for agent shells: commits get the co-author trailer of the model (server.commit_trailer).
+COPY --chmod=755 docker/git-coauthor /usr/local/lib/codecraft/bin/git
 COPY server/resources /app/resources
 # The agent's home lives on the data volume: tools it installs in user space
 # (pip --user, pipx, rustup, npm -g, downloaded binaries) survive rebuilds.