Fix newly outdated package notifications

[cch1rag]

Fixes #323

Summary

• compare refreshed outdated packages against the previous raw outdated set instead of the filtered displayable set
• keep the background notification subtitle limited to only newly outdated packages

Verification

• simulated the hidden-package scenario locally and confirmed only the genuinely new package is reported
• mise exec tuist@4.50.2 -- tuist generate
• xcodebuild -workspace Cork.xcworkspace -scheme Cork test -destination 'platform=macOS,arch=arm64' -derivedDataPath /tmp/CorkDerivedDataWorkspaceCork -clonedSourcePackagesDirPath /tmp/CorkSourcePackagesWorkspaceCork -skipPackagePluginValidation\n- swiftlint lint --no-cache --config .swiftlint.yml 'Cork/CorkApp.swift'

[buresdv]

Great, thank you very much for fixing this