fix(evaluator): Improve dispatcher claim throughput

[fuyu0425]

Summary

• derive dispatcher inflight headroom and claim batch size from local verify width and configured cloud evaluator count
• batch logical verify claims in Redis while preserving owner rotation semantics
• renew buffered batched claims before activation and add regression coverage for real cloud placement config shapes

Testing

• uv run pytest tests/test_evaluator_verify_claims.py tests/test_evaluator_claim_worker.py tests/test_evaluator_dual_queue.py
• scripts/ci-tests/run-local.sh checks

Notes

• rebased on origin/main before opening this PR
• multi-agent review surfaced and fixed evaluator-count and buffered-lease regressions