feat(review): post a quiet "review skipped (reason)" status when auto-review eligibility fails

[JSONbored]

Part of #1954. When decideReviewEligibility returns a skipReason, surface a quiet, non-blocking "review skipped (reason)" status/audit — never a gate failure (per the epic). This is the shared user-facing surface all predicate PRs feed into; map each skipReason to a human-readable summary line (mirror the SKIP_SUMMARY map in src/signals/settings-preview.ts:65).

Deliverables

• Add a REVIEW_SKIP_SUMMARY record mapping each review-eligibility skipReason to a public-safe sentence (mirror settings-preview SKIP_SUMMARY, src/signals/settings-preview.ts:65)
• At maybePublishPrPublicSurface (src/queue/processors.ts:4533), when a review-eligibility skip fires, emit the quiet status + an audit event (reuse the auditPrVisibilitySkip pattern, src/queue/processors.ts:4580) and DO NOT run the AI review; the gate verdict path is unaffected
• Ensure a skipped review never marks the gate check failed (assert in a test)
• Unit tests: each skipReason ⇒ correct summary + audit + no AI review + gate untouched; eligible ⇒ no skip status; 97% branch

References

• src/signals/settings-preview.ts:65
• src/queue/processors.ts:4580
• src/review/review-eligibility.ts
• #1954

Part of #1954.

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size: S · gittensor:feature

[linear-code]

JSO-2184