feat(agent-runner): enforce 4.x host-owned execution

src/langbot/templates/config.yaml

@@ -37,12 +37,6 @@ system:
         max_bots: -1
         max_pipelines: -1
         max_extensions: -1
-        # When set to a non-empty string, every pipeline is forced to use this
-        # Box sandbox-scope template regardless of its own configuration, and
-        # the per-pipeline "Sandbox Scope" selector is locked in the web UI.
-        # Used by SaaS deployments to confine a tenant to a single shared
-        # sandbox (set to '{global}'). Empty string = no restriction.
-        force_box_session_id_template: ''
     task_retention:
         # Keep at most this many completed async task records in memory
         completed_limit: 200