Second Phase 2 site migration. Hoists destination resolution out of
the per-iteration loop, uses a shared in_flight set so collision-prone
templates (%artist% on a page of same-artist posts) get sequential
suffixes instead of clobbering each other, and finally calls
_copy_library_thumb so multi-select bulk saves get library thumbnails
just like single-post saves do.
Drops the dead site_id assignment that nothing read.
Fixes the latent bug where _bulk_save left library thumbnails uncopied
even though _save_to_library always copied them — multi-select saves
were missing thumbnails in the Library tab until you re-saved one at
a time.
pax
b72f3a54c0