Add open source project metadata

CONTRIBUTING.md

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+# Contributing
+
+## Development Setup
+
+```bash
+python3 -m pip install -e .
+PYTHONPATH=src python3 -m unittest discover -s tests -v
+```
+
+## Change Requirements
+
+- Add or update tests for behavior changes.
+- Keep experiment claims tied to reproducible artifacts: study spec, trial spec,
+  result JSON, probe history, and per-request probe details.
+- Do not publish benchmark conclusions from bounded or time-compressed replays
+  without clearly labeling the replay controls.
+- Keep example configs free of private credentials and prefer explicit,
+  reproducible endpoint settings.
+
+## Commit Hygiene
+
+Use small commits grouped by behavior: measurement integrity, orchestration
+logic, documentation, or infrastructure.