perf(hop): traversal optimizations and fast path

[lmeyerov]

Summary

• add hop traversal fast path and domain-based visited/frontier tracking
• unify hop direction handling for simpler expansion
• add hop traversal tests for new paths

Stack

• Depends on: feat(otel): tracing helpers and header propagation #910
• Next: feat(gfql): add same-path WHERE executor #912 (same-path WHERE executor)

Testing

• uv run pytest graphistry/tests/compute/test_hop.py