feat(private-skills): add OpenClaw PR batch sweep

[vincentkoc]

What changed

• Added a private openclaw-pr-batch-sweep skill for strict batches of up to 20 contributor PRs.
• Encoded the operator's accepted/rejected patterns, no-padding rule, bounded sub-agent lanes, trusted-main execution boundary, and serial landing contract.
• Added a two-pass ranker with authoritative REST hydration, ClawSweeper label ranking, handled-set exclusion, high-risk/UI/security filtering, live-state/check validation, and adversarial input normalization.

Why

The existing OpenClaw landable-bug skill owned proof and landing but assumed exactly five results. This private skill keeps the operator-specific selection policy local while composing that canonical workflow.

Validation

• make validate
• make check-generated
• pre-commit run --all-files
• node --check private-skills/openclaw-pr-batch-sweep/scripts/rank-candidates.mjs
• Targeted fixtures for discovery vs hydrated selection, REST aliases, maintainer association, incomplete hydration, risk paths/titles, ClawSweeper labels, mergeability retries, latest check runs, snapshot-only changes, exclusions, and closed/dirty/failing PRs
• Fresh autoreview: clean, no actionable findings

Follow-up

After merge, sync the canonical main checkout into the local Codex and Cursor skill directories.