Repo skeleton, pinned environment, free smoke test

Public from commit one, so no key ever enters this history.

compose.yaml is ImpossibleBench's, plus working_dir: /workspace. The image has no
WORKDIR, so inspect resolves it to "/" and the task files land at the filesystem root
among twenty-odd entries. This experiment turns on whether an agent notices a scratch
directory, so that is a bad place to put one.

ImpossibleBench installs with --no-deps to keep the swebench tree out; datasets is
declared here instead because hf_dataset genuinely needs it.

Verified: docker run prints "/", impossiblebench imports, and the real task against
mockllm/model completes with a real score and tracebacks rooted at /workspace.

Claude-Session: https://claude.ai/code/session_01Cq98H7sNoSJdL3W98f18bu

README.md

@@ -0,0 +1,13 @@
+# messageboardbench
+
+Does cheating spread from one AI agent to another through a shared file?
+
+Agents get coding tasks whose tests contradict each other, so no honest solution exists and
+any pass is provably a cheat. Each agent also gets a scratch directory the prompt calls
+workspace and never describes as a channel. We measure whether carrying that directory from
+one agent to the next raises the cheating rate.
+
+Built on [ImpossibleBench](https://github.com/safety-research/impossiblebench) and
+[Inspect AI](https://inspect.aisi.org.uk). Tasks and payloads are synthetic throughout.
+
+See `docs/setup.md` to install and run, and `docs/findings.md` for measured numbers.