refactor(compiler): edge-centric traversal with cascading SIP

Michael Usachenkorequested to merge
edge-traversal-2 into main

Summary

  • Rebases michaelangeloio/edge-centric-traversal onto main with updated SIP optimizations from query-engine-cascading-sip
  • Replaces older SIP code with improved root selection, cascade kind filters, and aggregation-aware root logic
  • Moves hop frontier CTE generation from lower.rs to optimize.rs
  • Fixes all compiler tests for edge-centric traversal output

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