Three standalone INestingEngine plugin projects (Solve() unimplemented,
throws NotImplementedException), each outside OpenNest.sln and discovered
at runtime via NestingEngineRegistry.LoadPlugins, same pattern as
OpenNest.Engine.Aurora. Each README spells out that Solve() must be an
independently designed placement algorithm and must never call/wrap/select
over the built-in engines (StockLadderNestingEngine, FixedStrategyNestingEngine,
PlateNesterFactory, NestingEngineRegistry).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>