feat(infra): plumb FOXHUNT_USE_MULTI_HEAD_POLICY through alpha-rl template

Adds use-multi-head-policy workflow parameter (default "0") wired
into the container env block as FOXHUNT_USE_MULTI_HEAD_POLICY.
Adds --use-multi-head-policy flag to argo-alpha-rl.sh that passes
through to the workflow.

Enables Phase 2A-E cluster verification with the multi-head policy
mixture (commits 0b3e40150 → c8c81ab7e). Without this flag, the
cluster runs the legacy single-head path identical to pre-Phase-2A
behavior.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

infra/k8s/argo/alpha-rl-template.yaml

@@ -61,6 +61,8 @@ spec:
         value: "0"
       - name: nsys-profile
         value: "false"
+      - name: use-multi-head-policy
+        value: "0"
 
   volumes:
     - name: git-ssh-key
@@ -102,6 +104,8 @@ spec:
             value: /cargo-target/cargo-home
           - name: CARGO_INCREMENTAL
             value: "1"
+          - name: FOXHUNT_USE_MULTI_HEAD_POLICY
+            value: "{{workflow.parameters.use-multi-head-policy}}"
         resources:
           requests:
             cpu: "4"

scripts/argo-alpha-rl.sh

@@ -46,6 +46,7 @@ N_EVAL_STEPS=0
 WATCH=false
 SKIP_PUSH_CHECK=false
 SKIP_TEMPLATE_APPLY=false
+USE_MULTI_HEAD_POLICY=0
 
 usage() {
   cat <<EOF
@@ -109,6 +110,7 @@ while [[ $# -gt 0 ]]; do
     --watch)               WATCH=true; shift ;;
     --skip-push-check)     SKIP_PUSH_CHECK=true; shift ;;
     --skip-template-apply) SKIP_TEMPLATE_APPLY=true; shift ;;
+    --use-multi-head-policy) USE_MULTI_HEAD_POLICY="$2"; shift 2 ;;
     -h|--help)             usage; exit 0 ;;
     *) echo "Unknown option: $1"; usage; exit 1 ;;
   esac
@@ -221,4 +223,5 @@ argo submit -n foxhunt --from=wftmpl/alpha-rl \
   -p fold-idx="$FOLD_IDX" \
   -p n-folds="$N_FOLDS" \
   -p n-eval-steps="$N_EVAL_STEPS" \
+  -p use-multi-head-policy="$USE_MULTI_HEAD_POLICY" \
   $WATCH_FLAG