Emit gateway.start, gateway.ready, and gateway.shutdown on the shared runtime event bus, while keeping reload events on the same helper path.
Update subturn architecture docs to refer to runtime event kinds instead of the removed agent EventBus names.
Validation: GOCACHE=/tmp/picoclaw-go-cache go test ./pkg/gateway ./pkg/events; GOCACHE=/tmp/picoclaw-go-cache go test ./pkg/bus ./pkg/channels ./pkg/mcp ./pkg/tools/integration ./pkg/events ./pkg/gateway; make lint
Hoshina