Why: The product needs a session mode and a place to show tool arguments on a confirmation card without inventing a second card type.
Evidence: GOWORK=off go test . passed. New fields use omitempty, so existing golden JSON stays the same.
Impact: Empty permission mode still means the profile policy. Clients that ignore unknown fields keep working.
Refs: feature/permission-hooks
Co-authored-by: Cursor <cursoragent@cursor.com>