Test router with server_mode = true. Exercises server-mode-gated code paths such as
the locked watched-bar in trend-reports, path validation in analyze, and upload-only
preview restrictions.
Server-mode test router with allowed_scan_roots configured. Exercises the
validate_server_scan_path allow/deny branches (in-root success, unresolved
path, and out-of-root rejection) that the empty-roots router cannot reach.