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-K2.yaml

@@ -0,0 +1,15 @@
+# design 7 V-K2: known signature, VM. Delete one legacy instance; MIG autohealing recreates it (initial_delay 300s), ILB serves from the other.
+id: V-K2
+path: known
+asset: vm
+expected_layer: 1
+ground_truth_label: legacy_instance_lost
+ground_truth_action: none
+description: gcloud compute instances delete legacy instance 0
+escalate_after_s: 600
+inject:
+  method: gcloud
+  op: instance_delete
+  instance: legacy:0
+revert:
+  method: none