Verify candidate before smoke writes

[azurras]

Summary

• complete candidate legacy deletion and exact target verification before candidate application smoke traffic
• prevent disposable candidate runtime writes from invalidating the protected pre-smoke metric proof
• freeze the exact candidate operation order and document it

Production diagnosis

The guarded cutover repeatedly failed only in the disposable candidate database at drop-legacy: candidate smoke traffic had already created target-schema runtime records, so the exact evidence comparison correctly rejected deletion. Production rollback completed each time with legacyDropped=false and the legacy release healthy.

Verification

• focused RED captured smoke before candidate drop-legacy
• focused GREEN: 1/1 ordering regression
• owning orchestration PS7: 78/78
• owning orchestration PS5.1 + Pester 5.9: 78/78
• full PS7 production suite: 704 passed, 0 failed, 28 guarded skips
• Node migration contracts: 9/9
• PS7/PS5 parser and git diff --check: clean
• independent review: APPROVED, no Critical/Important findings