v0.3.0: PyPI debut

Install from PyPI, no clone, no git. The name shadowbox is now yours.

pipx install shadowbox

or per-run: uvx shadowbox --help

Onboard in one minute:

shadowbox init --out demo
cd demo (or stay; pass paths)
shadowbox validate model.yaml --scenario scenarios/db-failure.yaml
shadowbox simulate model.yaml --scenario cards/db-down.yaml --seed 42 --out report.json
shadowbox compare --a base.json --b report.json
shadowbox serve --port 8000

What is inside 0.3.0: deterministic seeded engine with golden hash, exact p50/p90/p95/p99, compose importer, 7 wheel-bundled chaos cards, local FastAPI server with SQLite, static demo with time-travel replay, React plus Cytoscape Studio source.

Full changelog: M0 contracts, M1 engine, M2 importer plus cards, M3 compare, M4a API, M4b cloud scaffold, M5a replay, M5b studio, serve command, init plus packaging, PyPI trusted publishing.