Add weighted affected traversal

[Ishaanb04]

Summary

• add relation-weighted affected traversal with optional hub penalties and budget-aware frontier scoring
• expose proof-path style traversal metadata for downstream evidence packets
• cover weighted traversal and existing affected CLI behavior with focused pytest coverage

Verification

• uv run --frozen pytest tests/test_affected_cli.py tests/test_weighted_affected.py -q --tb=short
• graphify update .