Fix MainForm callsite descriptions, clarify default implementations return empty lists, make FillExact non-virtual, document PackArea signature refactor, add AutoNester scope note, specify error handling for plugin loading, document thread safety and instance lifetime. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Pluggable engine architecture with NestEngineBase, DefaultNestEngine, registry with plugin loading, and global engine switching. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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