Replaces the material textbox on EditNestInfoForm with a combobox whose
items are aggregated from every loaded post processor that implements the
new IMaterialProvidingPostProcessor interface. CincinnatiPostProcessor
exposes its configured MaterialLibraries entries. Free-text entry still
works so custom materials remain usable.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
