Fix first domain cutover marker compatibility

[azurras]

What changed

• allow the first domain cutover to preserve a valid pre-existing Music schema marker when no prior domain-cutover state/history exists
• validate that marker through the exact production Music-marker reader before capture
• prove marker-first crash reconciliation restores the marker byte-for-byte
• reject malformed prior markers unchanged before publication

Root cause

Production legitimately has a version-1 Music schema marker from the earlier music migration, but no domain-cutover state. The prepublication binding validator incorrectly treated any prior marker without prior domain history as invalid.

Validation

• RED: 72 passed / 1 failed with First prepublication binding contains prior history
• focused PS7: 74/74
• focused Windows PowerShell 5.1 / Pester 5.9: 74/74
• full production Pester: 699 passed, 0 failed, 28 guarded skips
• parsers and git diff --check: clean
• independent review: APPROVED, 0 Critical / 0 Important / 0 Minor
• production failure was pre-effect; no marker/state/Mongo/service changes occurred