{% comment %} Mount marker — the server half of the dual-mode contract. Emitted for ts/_base/mount.ts's `mountPrefix()`, which throws when no marker is present rather than guessing a root mount. standalone_shell.html includes this in its ; a GUI that owns its own layout can include it directly the same way it includes _branding_head.html, with no shell adoption. The context comes from scitex_ui.mount.mount_context(request, view_path=...). WHY THE FLAG AND NOT `{% if stx_mount_prefix %}`: a root mount IS the empty string, so testing the value alone emits nothing in standalone mode — and "no marker" is what the reader treats as an integration bug. Mounted-at-root and nobody-declared-anything must not render identically. {% endcomment %}{% if stx_mount_declared %}{% endif %}