- REPEATS 10 → 2 (collection is index-keyed, so completion order can't drift; one run is

  mathematically sufficient, two is cheap insurance).
  - Dropped 13 redundant determinism cases — kept one per behavior (tied distances, repetition,
  exclude_paths, subtree rebasing, subtree add/remove keys, no recursive spawn, threshold gating).
  - Marked the 10 spawn-heavy tests @pytest.mark.slow so they only run under --runslow.
  - Kept all the helper/config unit tests in the fast path — they test the same fallback logic
  without paying spawn cost.

Author: seperman