CEX: search one admitted Binance replay with the shared MCTS kernel

[proerror77]

Parent

#205

What to build

Adapt the existing alpha-harness candidate search to the shared UCT/MCTS kernel for one admitted Binance time-series replay. Candidate generation, selection, and backpropagation must use training evidence only. After selection, run the existing held-out evaluator once and emit one research result receipt that binds the selected candidate, snapshot, search, evaluation, and checkpoint identities.

Acceptance criteria

• The adapter reuses hft-search-kernel and does not introduce a second MCTS implementation or modify the Polymarket evaluator.
• Search budget, stopping conditions, candidate identity, and deterministic tie-breaking are explicit and bound into the result evidence.
• Durable checkpoints bind the snapshot, search, evaluation, and candidate-space identities; a mismatched or stale checkpoint is rejected.
• Held-out rows and metrics are unavailable to candidate generation, selection, and backpropagation, and held-out evaluation runs only for the selected candidate.
• One bounded research-only run can resume from a valid checkpoint and emits a typed receipt with training evidence and the selected candidate held-out evidence.
• Focused counterexample tests prove held-out non-backpropagation and stale snapshot, protocol, or checkpoint rejection.

Blocked by

• CEX: evaluate an admitted Binance replay with purged post-cost walk-forward #401

[proerror77]

Implemented and merged by PR #413 at 399b330. All required CI gates and both independent read-only reviews passed.