Add from Drawing Library needs the same race-safe paging as the Database-mode
Open dialog: a generation counter so an older response never replaces a newer
one, cancellation after the superseding request is installed, and IsLoading
tracking only the latest request. `DrawingLibraryBrowseSession` mirrors
`NestBrowseSession` for library queries.
It starts filtered to the nest's material, grade and thickness, since that is
almost always what the operator wants and a mismatch drops cut pins anyway
(D3). "Show all" lifts the filter. A nest with no thickness filters by material
only, and the empty-result text tells the operator when the nest filter, rather
than an empty library, is why nothing is listed. Archived drawings stay hidden.
`IDrawingLibrary` is the read side the session and the add flow use, so both
are testable with fakes; `RemoteDrawingLibrary` implements it.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
