PostProcessorLoader and PostProcessorMaterials move unchanged (namespace
OpenNest kept) into the toolkit-neutral library, so the Avalonia app can
load the posts in Posts/ and register their materials as the WinForms app
does. Each DLL still loads on its own and a failing one is reported in the
result instead of stopping the others; the WinForms MainForm shows the
failures as before.
New tests load a copy of the test assembly as a post plug-in beside a
broken DLL: the broken one is reported, the good one's posts load and its
materials are registered once each, ignoring case and blanks.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
