When AppendSubtitle or AppendAlbumVersion is enabled, the subtitle/version
tag was always wrapped in parentheses and appended to the title/album name.
If the tag value already came wrapped in brackets (e.g. "(non-explicit
version)"), the result was doubled: "Title ((non-explicit version))".
Append the tag as-is when it is already wrapped in a matching bracket pair
- (), [], {} or <> - and trim surrounding whitespace first. The shared
appendSuffix helper is used by MediaFile.FullTitle, MediaFile.FullAlbumName
and Album.FullName so all consumers behave consistently.
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