Part.CloneAtOffset hands the copy the source's Program instance. The copy
cloned before rotating, but the source still owned the program, so rotating
the source turned the program under every tiled copy while their location
and bounds stayed put.
Program now carries a sticky SharedByParts flag that CloneAtOffset sets, and
a part copies its program before rotating when it does not own it or the
program is shared. The flag lives on the program rather than the part so a
restored cutting state, which reinstates ownership field for field, cannot
re-alias a shared program. Unrotated copies keep sharing one instance, which
the fill and overlap caches key on.
Update, ApplyLeadIns and ApplySingleLeadIn install a fresh program and now
own it, saving a needless copy on the next rotate.
Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>
