Adds two template params for the floating social icons sidebar:
- social_floating_collapsible: show/hide the collapse toggle handle
- social_floating_collapsed: start collapsed on first visit (default on)
The layout renders the initial collapsed state server-side (no flash),
gates the toggle button behind the collapsible param, and exposes the
admin default via data-default-collapsed. The JS honors a visitor's
saved localStorage preference first, falling back to the admin default.