Fix domain cutover snapshot consistency

[azurras]

Summary

• stop and suspend the legacy writer before backup and protected evidence capture
• use one quiesced snapshot for candidate proof and live destructive cutover
• restore the exact legacy release on stopped-snapshot initialization failure
• re-stop fail-closed if recovery normalization fails after legacy restart

Root cause

The legacy writer remained active between mongodump and protected preview. Application and maintenance lease renewals changed checksums, so the isolated candidate restored a backup that could never satisfy restore-verify against the later evidence.

Verification

• RED: orchestration 74/76, exact late-stop and missing recovery failures
• GREEN: focused PowerShell 7 77/77 and Windows PowerShell 5.1 77/77
• boundary suites: 292 passed, 1 environment-guarded skip
• full PowerShell 7: 702 passed, 28 guarded skips, 0 failed
• Node migration contracts: 9/9
• marker-owned Mongo matrix: 3/3, 0 skipped, including 468 interruption boundaries
• independent review: APPROVED, 0 Critical/Important