fix(ops): tolerate sparse uninstall entries

[azurras]

Summary

• ignore unrelated uninstall registry entries that omit DisplayName under strict PowerShell mode
• preserve exact one-package PostgreSQL 18.4-1 validation and legacy PostgreSQL rollback
• cover the production-host registry shape with a regression test

Verification

• focused PostgreSQL Pester: 28 passed
• complete production Pester: 767 passed, 28 expected environment skips
• Gradle PowerShell 7 production gate: 182 passed, 1 expected environment skip
• Gradle Windows PowerShell 5.1 production gate: 182 passed, 1 expected environment skip
• live read-only package enumeration: exact PostgreSQL 18.4-1 identity