The repo mixed variants such as center/centre and color/colour, so a
name could be spelled either way and searches missed half the hits.
Standardize on the US spelling, matching .NET's own APIs (Color, Center).
Wire values owned by other systems keep their spelling: the material
ledger's "Cancelled" hold status and GitHub's "cancelled" job status.
No behavior change beyond the spelling of a few status messages.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Document and Undo/ (ChangeScope, NestFingerprint, NestUndoState) use
only Core, Data, IO and Engine, so they move into the toolkit-neutral
library both desktop front ends share. Namespaces are unchanged, so the
WinForms app compiles as before; it keeps using the internal scope
factories and fingerprint through InternalsVisibleTo.
The scope, fingerprint and SaveAs/save-point rules now have Linux tests
in OpenNest.Desktop.Tests; before, only the Windows-only WinForms suite
covered them.