Move PR review completeness checks into planning and implementation #8555

Problem

Epic #8240 requires the same compact engineering checks during planning, implementation, and pull request review. PR #8533 added durable correctness guidance to PR follow-up, including root-cause grouping, adjacent-path inspection, and a sensitive-workflow state matrix. Those checks currently run only after a pull request opens.

PR #8545 routes valid review findings back to the implementation workflow. That gives repair work the correct owner, but it preserves the reactive loop: implementation completes, the pull request opens, review applies the missing guidance, and implementation repairs the result.

The first review cycle on PR #8545 exposed this gap:

• A routing evaluation assigned review collection and classification to the implementation stage.
• Triage writes trusted a user statement instead of repository-reported permission.
• A classified finding was treated as accepted product scope instead of a repair boundary inside accepted scope.

These defects were corrected after publication. Earlier use of the current ownership, authorization, and scope checks should have prevented them.

Current gap

• .agents/skills/_shared/pr-follow-up.md owns root-cause grouping, adjacent sibling-path inspection, and the sensitive-workflow state matrix.
• .agents/skills/_shared/code-change-considerations.md asks general state and failure questions but does not make those durable checks explicit for planning and implementation.
• nemoclaw-contributor-implement-issue applies the shared considerations during self-review, but its handoff does not record the sibling paths or sensitive state dimensions checked before editing.

Review evidence collection, pagination, head stability, comment disposition, and the push gate must remain PR-stage mechanics.

Expected behavior

Planning identifies applicable sibling operations, failure classes, and sensitive workflow states before implementation starts. Implementation applies those checks before editing and verifies them against the completed diff. PR follow-up consumes the same canonical checks without owning a separate copy.

Acceptance criteria

• One stage-neutral resource owns root-cause sibling-path inspection and the applicable sensitive-workflow state questions.
• Issue planning records the applicable operations, failure classes, state outcomes, trust boundaries, and expected evidence before implementation.
• Issue implementation records the sibling paths and sensitive state outcomes checked before editing and during self-review.
• PR follow-up retains review collection, head-stability, finding disposition, evidence cleanup, and push mechanics while consuming the shared checks.
• Planning, implementation, and review tests prove the same meanings without copying the guidance.
• Shared guidance contains no current path, command, selector, test, or architecture inventory.

Related work

• Parent epic: Use the same engineering checks during planning, implementation, and PR review #8240
• Contributor lifecycle consolidation: Complete the contributor lifecycle and fold component-specific routing #8364
• Follow-up implementation: PR refactor(skills): give each contributor lifecycle stage one owner #8545
• Maintainer workflow alignment remains tracked in Align maintainer PR workflows with shared code-change and security considerations #8365.