Add a crate-local mock executor over WorkflowSpec that records leaf, branch, and control-node results for Sequence, BranchSet, Leaf, Reduce, TeacherReview, LoopUntil, Cond, and Expand. Add reducer scaffolding for BranchTournament and ParetoFrontier, plus #2669 acceptance-style tests, without exposing workflow_run, spawning agents, or applying worktrees.
Refs #2669.
Harvests narrow WhaleFlow executor intent from #2482/#2486.
Co-authored-by: AdityaVG13 <44177453+AdityaVG13@users.noreply.github.com>
Hunter Bown
cfbaba722f