feat(graphml): export nested subgraphs in Classic GraphML

Слиты Зунин Владимир Викторович запросил слияние feat/graphml-classic-subgraphs в main

Summary

  • Export nested subgraphs in Classic GraphML with parent-port edges (ported from graphMLrework)
  • Add regression tests for nested subgraph XML and file write
  • Update GraphML/Subgraphs docs (ru/en) to match the new Classic behavior

Test plan

  • ctest --preset=dev (GraphML subgraph tests included)
  • Spot-check hierarchical vs unrolled Classic GraphML on a graph with 3+ subgraphs
Отредактировано пользователем Зунин Владимир Викторович