First slice of the maintainability refactor: golden-file characterization of behavior that later commits consolidate. The scope matrix runs every resolver (MeshMessage, resolve/effective_channel_send_scope, channel_body_budget, the scheduler's budget resolver, BaseServicePlugin.get_mesh_flood_scope, and the scopes a real send_channel_message hands to set_flood_scope) against 420 combinations of override, per-channel and section scope. The identity matrix runs each node-name lookup against every self_info shape. Both record today's divergences rather than fixing them, so a refactor commit that changes either golden file is a behavior change by definition.
