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

docs/setup.md

@@ -0,0 +1,54 @@
+# Setup
+
+Python 3.13 and a running Docker daemon. Everything the agent does happens in a container
+with the network disabled, so the daemon is not optional.
+
+```
+uv sync
+uv pip install -e /path/to/impossiblebench --no-deps
+```
+
+## Why --no-deps
+
+It is required, not a shortcut. ImpossibleBench declares
+`inspect_evals[swe_bench] @ git+https://github.com/UKGovernmentBEIS/inspect_evals` from
+unpinned git main, which forces `huggingface_hub` up to 1.2+, and `swebench>=4.0.0`, which
+drags `modal`, `GitPython`, `typer` and `pre-commit` in as runtime dependencies.
+
+The LiveCodeBench path we use imports none of it. Every `swebench` import in that package is
+lazy and inside a function, and `inspect_evals` is declared but never imported.
+
+`--no-deps` also skips `datasets`, which `hf_dataset` genuinely does need, so this repo
+declares that one itself in `pyproject.toml`.
+
+Two things to know. `uv sync` prunes ImpossibleBench, because it is not declared in
+`pyproject.toml`, so rerun the install line after every sync. `just install` does both.
+And ImpossibleBench mutates `sys.path` at import time to paper over a broken import, which
+loads some modules twice, so do not trust module identity inside it.
+
+## The working directory
+
+`compose.yaml` at the repo root sets `working_dir: /workspace`, which is a deliberate
+deviation from the published benchmark. The file itself explains why.
+
+Inspect looks for `compose.yaml` in the **process working directory**, not next to the task
+definition, so every command has to run from the repo root. If you run from somewhere else
+you silently get ImpossibleBench's own compose file, and the working directory reverts to
+`/`. The justfile recipes handle this.
+
+## Checks that cost nothing
+
+```
+just smoke      # the real task against a fake model, exercises everything but the model
+just test       # offline unit tests, no network and no provider beyond mockllm
+```
+
+`just smoke` should end with `status: success` and a real score. If the tracebacks in that
+score mention `/workspace/test.py`, the working directory override is live.
+
+## Spending money
+
+`.env` holds `OPENROUTER_API_KEY` and is gitignored. The key carries a $2 cap as a fuse.
+
+Watch per-request `prompt_n` on any run longer than a few turns. Cache reuse fails silently
+and costs 8 to 18 times as much without emitting an error.