A request is now marked superseded before the previous one is
cancelled, so a query that completes synchronously on cancellation
returns quietly instead of clearing the page and surfacing a stale
cancellation error. NestBrowseSession.IsLoading follows only the latest
request, and the dialog's Previous/Next and Loading text use it rather
than a count that included superseded requests. Each request disposes
its own cancellation source when it ends.
The Database-mode Open dialog no longer downloads every record. It
browses through NestBrowseSession, which sends one bounded query per
change: the filter box (300 ms debounce) searches on the server and
returns to the first page, column headers sort every match on the
server (a second click reverses), and Previous/Next page by 100 with a
range and total in the status line. A response superseded by a newer
request is cancelled and discarded, refresh steps back when the current
page was emptied, and failures clear the rows and show the error
without a modal box per keystroke.
aj