fix(conformance): block-style chainsaw checks (flow-map broke on contains comma)

My previous commit converted =~ to contains() but kept flow style
'check: { (contains($stdout, 'X')): true }' — the comma inside contains() is a
YAML flow-map separator, so 9 tests failed yamllint ('expected , or }'). Convert
those checks to block style (matching data-survival), where a comma in the key
scalar is fine. Gate PASS; data-survival still green.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

conformance/tests/l2-behavioral/sso-forward-auth/chainsaw-test.yaml

@@ -37,7 +37,8 @@ spec:
                 curl -s -o /dev/null -w '%{http_code}' https://<service>.home.keithjackson.dev)
               echo "unauth_code=$code"
               case "$code" in 302|303|401|403) echo CHALLENGED_OK ;; *) exit 1 ;; esac
-            check: { (contains($stdout, 'CHALLENGED_OK')): true }
+            check:
+              (contains($stdout, 'CHALLENGED_OK')): true
     - name: then-authenticated-is-granted
       try:
         - script: