feat: harness VM stack (runner, measure-db, blackbox, Alloy, k6) and the 12 scenarios

Experiment design 5 and 7 for the harness VM (10.20.0.11): vm/harness/apply.sh pulls the secrets from Secret Manager,
compose runs runner:de076a7, measure-db, blackbox, Alloy (probe_success -> Mimir) and k6 under the campaign profile.
Scenario files C-K1..X-M2 are loaded by the runner. Harness ClusterRole gains replicasets get/list for rollout undo.

vm/harness/scenarios/V-I1.yaml

@@ -0,0 +1,15 @@
+# design 7 V-I1: irreversible, VM. Stop db-primary. Layer 2 diagnoses -> escalate -> a human promotes the replica and switches the DSN (db.promote).
+# The old primary is not started again (STONITH); revert is none by design. Recovery of the lab afterwards: Terraform / restore.
+id: V-I1
+path: irreversible
+asset: vm
+expected_layer: 3
+ground_truth_label: db_primary_down
+ground_truth_action: escalate
+description: gcloud compute instances stop selfheal-db-primary
+inject:
+  method: gcloud
+  op: instance_stop
+  instance: db-primary
+revert:
+  method: none