fix: windows save dialog extension bug

* fix: windows save dialog extension bug

* refactor: simplify firstSpec extraction

Co-authored-by: Charles Kerr <charles@charleskerr.com>

* refactor: split when necessary

Co-authored-by: Sam Maddock <samuel.maddock@gmail.com>

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Co-authored-by: Charles Kerr <charles@charleskerr.com>
Co-authored-by: Sam Maddock <samuel.maddock@gmail.com>

Co-authored-by: nilaoda <nilaoda@live.com>