test: let a fixture declare its own workflow settings
Storage-touching nodes are permission-checked against
workflow.settings.storagePermissions, but the harness always created
workflows with an empty settings object, so any node calling
smartbotic.storage.* failed with a permission error inside every
harness-created workflow. Let case.get("settings", {}) pass through
instead of hardcoding {}; every existing fixture omits the key and is
unaffected.