This PR implements transitive reduction for directed acyclic graphs (#1978).

Implementation notes

• The algorithm removes redundant edges u→x whenever an alternative path u→v→…→x exists, preserving reachability by construction.
• It processes each node’s successors incrementally and performs pruned DFS from each successor to detect transitive edges.
• To scale to larger and denser DAGs, the implementation uses:
  • Dense node indexing with generation counters to track reachability and visited state without repeated clearing.
  • Reused scratch buffers to minimize allocations and GC pressure.

Result

• Provides a single, optimized implementation.
• Benchmarks show reduced runtime, memory usage, and allocations relative to an earlier implementation developed during this work (commit 4a33fa6), especially for dense graphs.

Fixes #1978