M0: workspace and test primitives

The native fixture server provides HTTP diagnostics, WebSocket echo, SSE and process-lifecycle controls. devlanes-testing supplies test-owned homes and Git repositories. CI is configured for macOS and Linux; hosted runs must establish platform acceptance.

Run from the repository root:

cargo run -p devlanes -- --version
cargo test -p devlanes-testing
cargo run -p devlanes-testing --bin fixture-server -- --port 4999 --exit-after 10s

While the fixture is running, in another terminal:

curl -fsS http://127.0.0.1:4999/healthz
curl -N --max-time 2 http://127.0.0.1:4999/sse

The SSE command intentionally ends at curl’s timeout. WebSocket clients can connect to ws://127.0.0.1:4999/ws for text/binary echo.