fix(spec): improve prover-verifier iteration

[rohangpta]

Summary

• guide provers toward coherent, tested checkpoints before evaluation
• prioritize current evaluator findings and high-leverage unmet obligations
• let verifiers reuse valid evidence and extend durable probes
• read recent transcript state first while retaining older history for uncertainty

Validation

• go build ./...
• go vet ./...
• go test ./...
• go test -race ./...