diag: enable FOXHUNT_NO_GRAPH in Argo train template — isolate H100 graph issue

Temporarily sets FOXHUNT_NO_GRAPH=1 in train-best pods to run
forward+backward+Adam ungraphed. If grad_buf is non-zero ungraphed,
the root cause is CUDA Graph capture of cuBLASLt on H100 SM90.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

infra/k8s/argo/train-template.yaml

@@ -400,6 +400,8 @@ spec:
             value: ":4096:8"
           - name: FOXHUNT_FEATURE_CACHE_DIR
             value: /feature-cache
+          - name: FOXHUNT_NO_GRAPH
+            value: "1"
         resources:
           requests:
             nvidia.com/gpu: "1"
@@ -484,6 +486,8 @@ spec:
             value: ":4096:8"
           - name: FOXHUNT_FEATURE_CACHE_DIR
             value: /feature-cache
+          - name: FOXHUNT_NO_GRAPH
+            value: "1"
         resources:
           requests:
             nvidia.com/gpu: "1"