Fix PostgreSQL cutover evidence parsing

[azurras]

Summary

• extract exactly one command-specific PostgreSQL cutover evidence record from Java stdout
• ignore unrelated MongoDB/Java log lines without weakening evidence validation
• fail closed for missing, malformed, or duplicated evidence

Root cause

The standalone MongoDB Java client writes informational log lines to stdout. The cutover wrapper previously required the entire stdout stream to equal the machine-evidence record, so valid production snapshot evidence was rejected before authority publication.

Validation

• TDD RED: six focused cases reproduced logged, missing, malformed, and duplicate output failures
• focused Pester: 26 passed, 0 failed
• full Windows production operations: 787 passed, 0 failed, 28 skipped
• independent review: no findings; ready to merge