fix: dedupe GitHub PR review webhooks

[RND-Agent]

Summary

• Gate Codex/RND-Agent PR-review lifecycle suppression behind github_pr_review_dedupe: true so generic GitHub webhook routes are unaffected.
• Add same-head review dedupe before launching an agent, using prior RND-Agent ## Code Review Summary reviews without requiring newer artifact markers.
• Move delivery-id idempotency before review/head lookups so GitHub retries do not repeatedly run synchronous gh api checks.
• Cover lifecycle no-op, same-head CHANGES_REQUESTED dedupe, generic route pass-through, deliver-only pass-through, and duplicate-delivery fast path.

Request Source / Audit

• Requested by: Simon Shao via Slack thread.
• Request source: Slack thread discussing duplicate output on Mesitis/alphapulse PR Update dependencies and enhance installation scripts #16.
• Original request: "修正" after review concluded duplicate same-head RND-Agent PR reviews were not reasonable.
• Related link: https://github.com/Mesitis/alphapulse/pull/16

Change Source

• Change type: agent-authored fix with Codex-assisted implementation and review.
• Source branch: origin/main
• Source commit: 8d3c45012
• New commit: 94ea3a7fc66829ef51cd1a51c2f08f3a350469ce

Target

• Repo: NousResearch/hermes-agent
• Base branch: main
• Head branch: RND-Agent:fix/pr-review-lifecycle-dedupe
• Environment: Hermes webhook GitHub PR-review automation.

Changed Files

• gateway/platforms/webhook.py: adds opt-in PR-review lifecycle suppression, same-head review dedupe, and earlier delivery-id idempotency.
• tests/gateway/test_webhook_integration.py: adds regression coverage for PR-review dedupe and generic route non-regression cases.

Validation

• python -m pytest tests/gateway/test_webhook_integration.py tests/gateway/test_webhook_adapter.py tests/gateway/test_webhook_signature_rate_limit.py tests/gateway/test_webhook_dynamic_routes.py tests/gateway/test_webhook_deliver_only.py -q -> 109 passed.
• git diff --check -> passed.
• Codex review of first pass found over-broad generic webhook impact and idempotency ordering; follow-up fix addressed those findings.

Risk / Rollback

• Risk: medium-low; behavior is opt-in through github_pr_review_dedupe: true, but the opted-in GitHub PR-review route must have this flag set to activate dedupe.
• Rollback: revert this PR to restore previous webhook dispatch behavior.