Add Items to a Booking That's Already Underway

Plans change after gear starts leaving the cage. Now you can add assets and kits to a booking that's already Ongoing or Overdue, right from the asset page, a kit page, the booking's own Manage assets modal, the bulk Add to booking panel, and both scanners.

The new items join the booking as line items and stay Available until you purposefully check them out. That matches how progressive checkout already works: the booking is "open" from the first item that leaves, and you keep handing gear out as it's picked up. Adding something mid-booking no longer forces it into a checked-out state you didn't ask for.

Shelf still protects you from double-booking: an item that's already checked out on another active booking can't be pulled onto this one. Everything else is fair game to add whenever you need it.